NN Scattering Phase Shifts in a Chiral Constituent Quark Model
Bartz, D.; Stancu, Fl
2000-01-01
We study the nucleon-nucleon interaction within a chiral constituent quark model which reproduces succesfully the baryon spectra. We calculate the 3S1 and 1S0 phase shifts by using the resonating group method. They clearly indicate the presence of a strong repulsive interaction at short distance, due to the spin-flavor symmetry of the quark-quark interaction and of the quark interchange between the two interacting nucleons. A sigma-exchange quark-quark interaction, providing a medium-range at...
Thermodynamics of Constituent Quarks
Pirner, H. J.; Wachs, M
1997-01-01
We investigate the thermal behavior of quarks and antiquarks interacting via a temperature-dependent linear potential. The quarks are constituent quarks with dynamically generated masses from the background linear $\\sigma$-model.We find a transition from a system of bound mesons to a correlated quark gas at the same temperature as the chiral transition temperature.
Pion- and strangeness-baryon $\\sigma$ terms in the extended chiral constituent quark model
An, C. S.; Saghai, B.
2014-01-01
Within an extended chiral constituent quark formalism, we investigate contributions from all possible five-quark components in the octet baryons to the pion-baryon ($\\sigma_{\\pi B}$) and strangeness-baryon ($\\sigma_{s B}$) sigma terms; $B \\equiv N,~\\Lambda,~\\Sigma,~\\Xi$. The probabilities of the quark-antiquark components in the ground-state baryon octet wave functions are calculated by taking the baryons to be admixtures of three- and five-quark components, with the relevant transitions hand...
Hadronic contributions to the muon anomaly in the Constituent Chiral Quark Model
Greynat, David
2016-04-01
The hadronic contributions to the anomalous magnetic moment of the muon which are relevant for the confrontation between theory and experiment at the present level of accuracy, are evaluated within the same framework: the constituent chiral quark model. This includes the contributions from the dominant hadronic vacuum polarization as well as from the next-to-leading order hadronic vacuum polarization, the contributions from the hadronic light-by-light scattering, and the contributions from the electroweak hadronic Zγγ vertex. They are all evaluated as a function of only one free parameter: the constituent quark mass. We also comment on the comparison between our results and other phenomenological evaluations.
Nucleon structure functions and longitudinal spin asymmetries in the chiral quark constituent model
Dahiya, Harleen
2016-01-01
We have analysed the phenomenological dependence of the spin independent ($F_1^{p,n}$ and $F_2^{p,n}$) and the spin dependent ($g_1^{p,n}$) structure functions of the nucleon on the the Bjorken scaling variable $x$ using the unpolarized distribution functions of the quarks $q(x)$ and the polarized distribution functions of the quarks $\\Delta q(x)$ respectively. The chiral constituent quark model ($\\chi$CQM), which is known to provide a satisfactory explanation of the proton spin crisis and related issues in the nonperturbative regime, has been used to compute explicitly the valence and sea quark flavor distribution functions of $p$ and $n$. In light of the improved precision of the world data, the $p$ and $n$ longitudinal spin asymmetries ($A_1^p(x)$ and $A_1^n(x)$) have been calculated. The implication of the presence of the sea quarks has been discussed for ratio of polarized to unpolarized quark distribution functions for up and down quarks in the $p$ and $n$ $\\frac{\\Delta u^p(x)}{u^p(x)}$, $\\frac{\\Delta d...
Nucleon structure functions and longitudinal spin asymmetries in the chiral quark constituent model
Dahiya, Harleen; Randhawa, Monika
2016-06-01
We have analyzed the phenomenological dependence of the spin independent (F1p ,n and F2p ,n) and the spin dependent (g1p ,n) structure functions of the nucleon on the Bjorken scaling variable x using the unpolarized distribution functions of the quarks q (x ) and the polarized distribution functions of the quarks Δ q (x ) respectively. The chiral constituent quark model, which is known to provide a satisfactory explanation of the proton spin crisis and related issues in the nonperturbative regime, has been used to compute explicitly the valence and sea quark flavor distribution functions of p and n . In light of the improved precision of the world data, the p and n longitudinal spin asymmetries [A1p(x ) and A1n(x )] have been calculated. The implication of the presence of the sea quarks has been discussed for the ratio of polarized to unpolarized quark distribution functions for up and down quarks in the p and n Δ/up(x ) up(x ) , Δ/dp(x ) dp(x ) , Δ/un(x ) un(x ) , and Δ/dn(x ) dn(x ) . The ratio of the n and p structure functions Rn p(x )=F/2n(x ) F2p(x ) has also been presented. The results have been compared with the recent available experimental observations. The results on the spin sum rule have also been included and compared with data and other recent approaches.
Nucleon shape and electromagnetic form factors in the chiral constituent quark model
Dahiya, Harleen
2010-01-01
The electromagnetic form factors are the most fundamental quantities to describe the internal structure of the nucleon and the shape of a spatially extended particle is determined by its intrinsic quadrupole moment which can be related to the charge radii. We have calculated the electromagnetic form factors, nucleon charge radii and the intrinsic quadrupole moment of the nucleon in the framework of chiral constituent quark model. The results obtained are comparable to the latest experimental studies and also show improvement over some theoretical interpretations.
Charge radii of octet and decuplet baryons in chiral constituent quark model
Indian Academy of Sciences (India)
Neetika Sharma; Harleen Dahiya
2013-09-01
The charge radii of the spin-$\\dfrac{1}{2}^{+}$ octet and spin-$\\dfrac{3}{2}^{+}$ decuplet baryons have been calculated in the framework of chiral constituent quark model ( CQM) using a general parametrization method (GPM). Our results are not only comparable with the latest experimental studies but also agree with other phenomenological models. The effects of (3) symmetry breaking pertaining to the strangeness contribution and GPM parameters pertaining to the one-, two- and three-quark contributions have also been investigated in detail and are found to be the key parameters in understanding the non-zero values for the neutral octet $(n, \\sum^{0}, \\Xi, )$ and decuplet $(^{0}, \\sum^{*0}, \\Xi^{*0})$ baryons.
Topological and nontopological solutions for the chiral bag model with constituent quarks
International Nuclear Information System (INIS)
The three-phase version of the hybrid chiral bag model, containing the phase of asymptotic freedom, the hadronization phase as well as the intermediate phase of constituent quarks is proposed. For this model the self-consistent solutions of different topology are found in (1 + 1)D with due regard for fermion vacuum polarization effects. The renormalized total energy of the bag is studied as a function of its geometry and topological charge. It is shown that in the case of nonzero topological charge there exists a set of configurations being the local minima of the total energy of the bag and containing all the three phases, while in the nontopological case the minimum of the total energy of the bag corresponds to vanishing size of the phase of asymptotic freedom
Current and constituent quark masses
International Nuclear Information System (INIS)
It is shown how the current quark mass, engendered by the electroweak sector, gives rise to a constituent quark mass, via the Dyson-Schwinger equations. The chiral symmetry breaking phenomenon on massless QCD is thereby seen to have an implementable generalization to the situation in which the strong bare mass is non-zero. A consistent renormalization is carried out for an arbitrary covariant gauge. (author). 16 refs
Hyperon polarization in the constituent quark model
International Nuclear Information System (INIS)
A mechanism for hyperon polarization in the inclusive production is considered. The main role belongs to the orbital angular momentum and polarization of strange quark-antiquark pairs in the internal structure of constituent quarks. The nonperturbative hadron structure is based on the results of chiral quark models
Indian Academy of Sciences (India)
H Weigel
2003-11-01
In this talk I review studies of hadron properties in bosonized chiral quark models for the quark ﬂavor dynamics. Mesons are constructed from Bethe–Salpeter equations and baryons emerge as chiral solitons. Such models require regularization and I show that the two-fold Pauli–Villars regularization scheme not only fully regularizes the effective action but also leads the scaling laws for structure functions. For the nucleon structure functions the present approach serves to determine the regularization prescription for structure functions whose leading moments are not given by matrix elements of local operators. Some numerical results are presented for the spin structure functions.
A chiral symmetric quark model without free quarks
International Nuclear Information System (INIS)
A chirally symmetric quark model is presented which contrary to the Nambu Jona-Lasinio (NJL) model does not lead to the presence of free quarks. In the model a non-local effective interaction is used as a schematic parameterization of the quark antiquark scattering kernel. The non-locality can be interpreted as phenomenologically taking into account an infinite number of elementary scattering processes, like the sum of all multi-gluon exchange processes in the particle-particle channel. The basic Lagrangian of the interaction shares all global internal symmetries with QCD. In particular in the limit of vanishing current quark masses it is chirally symmetric. Starting from the non-local scattering kernel the solution of the Dyson-Schwinger equation and the Bethe-Salpeter equation leads to a consistent description of the dressed quark propagators with the mesonsa s quark-antiquark states. Like in the NJL-model chiral symmetry is spontaneously broken. Because of the non-locality of the interaction, however, in our model the quarks do not acquire a constant constituent mass but a four momentum dependent selfenergy. (orig.)
Quarks, baryons and chiral symmetry
Hosaka, Atsushi
2001-01-01
This book describes baryon models constructed from quarks, mesons and chiral symmetry. The role of chiral symmetry and of quark model structure with SU(6) spin-flavor symmetry are discussed in detail, starting from a pedagogic introduction. Emphasis is placed on symmetry aspects of the theories. As an application, the chiral bag model is studied for nucleon structure, where important methods of theoretical physics, mostly related to the semiclassical approach for a system of strong interactions, are demonstrated. The text is more practical than formal; tools and ideas are explained in detail w
Hadronic interactions from effective chiral Lagrangians of quarks and gluons
International Nuclear Information System (INIS)
We discuss the combined used of the techniques of effective chiral field theory and the field theoretic method known as Fock-Tani representation to derive effective hadron interactions. The Fock-Tani method is based on a change of representation by means of a unitary transformation such that the composite hadrons are redescribed by elementary-particle field operators. Application of the unitary transformation on the microscopic quark-quark interaction derived from a chiral effective Lagrangian leads to chiral effective interactions describing all possible processes involving hadrons and their constituents. The formalism is illustrated by deriving the one-pion-exchange potential between the nucleons using the quark-gluon effective chiral Lagrangian of Manohar and Georgi. We also present the results of a study of the saturation properties of the nuclear matter using this formalism. (author). 9 refs., 2 figs
Dimension 2 condensates and Polyakov Chiral Quark Models
Megias, E.; Arriola, E. Ruiz; Salcedo, L. L.
2006-01-01
We address a possible relation between the expectation value of the Polyakov loop in pure gluodynamics and full QCD based on Polyakov Chiral Quark Models where constituent quarks and the Polyakov loop are coupled in a minimal way. To this end we use a center symmetry breaking Gaussian model for the Polyakov loop distribution which accurately reproduces gluodynamics data above the phase transition in terms of dimension 2 gluon condensate. The role played by the quantum and local nature of the ...
Lattice QCD with dynamical chirally improved quarks
International Nuclear Information System (INIS)
Full text: We simulate lattice QCD with two flavors of chirally improved dynamical (sea) quarks. The chirally improved lattice action allows to address some of the questions concerning chiral symmetry in lattice QCD.We discuss the status and prospects of our simulations as well as recent results. (author)
Mesons in the Constituent Quark Model
Institute of Scientific and Technical Information of China (English)
WANG Li; PING Jia-Lun
2007-01-01
The quark-antiquark (q(-q)) spectrum is studied by solving the Schrǒdinger equation in the framework of non-relativistic constituent quark model. An overall good fit to the experimental data of meson is obtained. The interactions between quark and antiquark consist of quadratic colour confinement-exchange, one-gluon-exchange, and Goldstone-boson-exchange potentials.
Gluonic Structure of the Constituent Quark
Kochelev, Nikolai; Zhang, Baiyang; Zhang, Pengming
2015-01-01
Based on both the constituent quark picture and the instanton model for QCD vacuum, we calculate the unpolarized and polarized gluon distributions in the constituent quark and in the nucleon. Our approach consists of the two main steps. At the first step, we calculate the gluon distributions inside the constituent quark generated by the perturbative quark-gluon interaction, the non-perturbative quark-gluon interaction, and the non-perturbative quark-gluon-pion anomalous chromomagnetic interaction. The non-perturbative interactions are related to the existence of the instantons, strong topological fluctuations of gluon fields, in the QCD vacuum. At the second step, the convolution model is applied to derive the gluon distributions in the nucleon. A very important role of the pion field in producing the unpolarized and the polarized gluon distributions in the hadrons is discovered. We discuss a possible solution of the proton spin problem.
Gluonic structure of the constituent quark
Kochelev, Nikolai; Lee, Hee-Jung; Zhang, Baiyang; Zhang, Pengming
2016-06-01
Based on both the constituent quark picture and the instanton model for QCD vacuum, we calculate the unpolarized and polarized gluon distributions in the constituent quark and in the nucleon. Our approach consists of the two main steps. At the first step, we calculate the gluon distributions inside the constituent quark generated by the perturbative quark-gluon interaction, the non-perturbative quark-gluon interaction, and the non-perturbative quark-gluon-pion anomalous chromomagnetic interaction. The non-perturbative interactions are related to the existence of the instantons, strong topological fluctuations of gluon fields, in the QCD vacuum. At the second step, the convolution model is applied to derive the gluon distributions in the nucleon. A very important role of the pion field in producing the unpolarized and the polarized gluon distributions in the hadrons is discovered. We discuss a possible solution of the proton spin problem.
Parity doublers in chiral potential quark models
International Nuclear Information System (INIS)
The effect of spontaneous breaking of chiral symmetry over the spectrum of highly excited hadrons is addressed in the framework of a microscopic chiral potential quark model (Generalised Nambu-Jona-Lasinio model) with a vectorial instantaneous quark kernel of a generic form. A heavy-light quark-antiquark bound system is considered, as an example, and the Lorentz nature of the effective light-quark potential is identified to be a pure Lorentz-scalar, for low-lying states in the spectrum, and to become a pure spatial Lorentz vector, for highly excited states. Consequently, the splitting between the partners in chiral doublets is demonstrated to decrease fast in the upper part of the spectrum so that neighboring states of an opposite parity become almost degenerate. A detailed microscopic picture of such a 'chiral symmetry restoration' in the spectrum of highly excited hadrons is drawn and the corresponding scale of restoration is estimated
Chiral transition of fundamental and adjoint quarks
Capdevilla, R. M.; Doff, A.(Universidade Tecnológica Federal do Paraná – UTFPR – DAFIS, Av. Monteiro Lobato Km 04, 84016-210 Ponta Grossa, PR, Brazil); Natale, A. A.
2014-01-01
The chiral symmetry breaking transition of quarks in the fundamental and adjoint representation is studied in a model where the gap equation contains two contributions, one containing a confining propagator and another corresponding to the exchange of one-dressed dynamically massive gluons. When quarks are in the fundamental representation the confinement effect dominates the chiral symmetry breaking while the gluon exchange is suppressed due to the dynamical gluon mass effect in the propagat...
Confined Chiral Solitons in the Spectral Quark Model
Ruiz-Arriola, E; Golli, B; Arriola, Enrique Ruiz; Broniowski, Wojciech; Golli, Bojan
2006-01-01
Chiral solitons with baryon number one are investigated in the spectral quark model. In this model the quark propagator is a superposition of complex mass propagators with a suitable spectral function. As a result, the constituent quark mass is identified with saddle points of the Dirac eigenvalues. Due to this feature the valence quarks never become unbound nor dive into the negative spectrum, hence providing stable solitons as absolute minima of the action. This a manifestation of the built-in analytic confinement in the spectral quark model. Self-consistent mean field hedgehog solutions are found and some of their properties determined. Our analysis constitutes an example of a treatment of a relativistic complex mass system.
Chiral transition of fundamental and adjoint quarks
Energy Technology Data Exchange (ETDEWEB)
Capdevilla, R.M. [Instituto de Física Teórica, UNESP – Universidade Estadual Paulista, Rua Dr. Bento T. Ferraz, 271, Bloco II, 01140-070 São Paulo, SP (Brazil); Doff, A., E-mail: agomes@utfpr.edu.br [Universidade Tecnológica Federal do Paraná – UTFPR – DAFIS, Av. Monteiro Lobato Km 04, 84016-210 Ponta Grossa, PR (Brazil); Natale, A.A., E-mail: natale@ift.unesp.br [Instituto de Física Teórica, UNESP – Universidade Estadual Paulista, Rua Dr. Bento T. Ferraz, 271, Bloco II, 01140-070 São Paulo, SP (Brazil); Centro de Ciências Naturais e Humanas, Universidade Federal do ABC, 09210-170 Santo André, SP (Brazil)
2014-01-20
The chiral symmetry breaking transition of quarks in the fundamental and adjoint representation is studied in a model where the gap equation contains two contributions, one containing a confining propagator and another corresponding to the exchange of one-dressed dynamically massive gluons. When quarks are in the fundamental representation the confinement effect dominates the chiral symmetry breaking while the gluon exchange is suppressed due to the dynamical gluon mass effect in the propagator and in the coupling constant. In this case the chiral and deconfinement transition temperatures are approximately the same. For quarks in the adjoint representation, due to the larger Casimir eigenvalue, the gluon exchange is operative and the chiral transition happens at a larger temperature than the deconfinement one.
Chiral transition of fundamental and adjoint quarks
International Nuclear Information System (INIS)
The chiral symmetry breaking transition of quarks in the fundamental and adjoint representation is studied in a model where the gap equation contains two contributions, one containing a confining propagator and another corresponding to the exchange of one-dressed dynamically massive gluons. When quarks are in the fundamental representation the confinement effect dominates the chiral symmetry breaking while the gluon exchange is suppressed due to the dynamical gluon mass effect in the propagator and in the coupling constant. In this case the chiral and deconfinement transition temperatures are approximately the same. For quarks in the adjoint representation, due to the larger Casimir eigenvalue, the gluon exchange is operative and the chiral transition happens at a larger temperature than the deconfinement one
Two chiral nonet model with massless quarks
International Nuclear Information System (INIS)
We present a detailed study of a linear sigma model containing one chiral nonet transforming under U(1)A as a quark-antiquark composite and another chiral nonet transforming as a diquark-antidiquark composite (or, equivalently from a symmetry point of view, as a two meson molecule). The model provides an intuitive explanation of a current puzzle in low energy QCD: Recent work has suggested the existence of a lighter than 1 GeV nonet of scalar mesons which behave like four quark composites. On the other hand, the validity of a spontaneously broken chiral symmetric description would suggest that these states be chiral partners of the light pseudoscalar mesons, which are two quark composites. The model solves the problem by starting with the two chiral nonets mentioned and allowing them to mix with each other. The input of physical masses in the SU(3) invariant limit for two scalar octets and an excited pion octet results in a mixing pattern wherein the light scalars have a large four quark content while the light pseudoscalars have a large two quark content. One light isosinglet scalar is exceptionally light. In addition, the pion pion scattering is also studied and the current algebra theorem is verified for massless pions which contain some four quark admixture
Chiral dynamics of baryons in the perturbative chiral quark model
Energy Technology Data Exchange (ETDEWEB)
Pumsa-ard, K.
2006-07-01
In this work we develop and apply variants of a perturbative chiral quark model (PCQM) to the study of baryonic properties dominantly in the low-energy region. In a first step we consider a noncovariant form of the PCQM, where confinement is modelled by a static, effective potential and chiral corrections are treated to second order, in line with similar chiral quark models. We apply the PCQM to the study of the electromagnetic form factors of the baryon octet. We focus in particular on the low-energy observables such as the magnetic moments, the charge and magnetic radii. In addition, the electromagnetic N-delta transition is also studied in the framework of the PCQM. In the chiral loop calculations we consider a quark propagator, which is restricted to the quark ground state, or in hadronic language to nucleon and delta intermediate states, for simplicity. We furthermore include the low-lying excited states to the quark propagator. In particular, the charge radius of the neutron and the transverse helicity amplitudes of the N-delta transition are considerably improved by this additional effect. In a next step we develop a manifestly Lorentz covariant version of the PCQM, where in addition higher order chiral corrections are included. The full chiral quark Lagrangian is motivated by and in analogy to the one of Chiral Perturbation Theory (ChPT). This Lagrangian contains a set of low energy constants (LECs), which are parameters encoding short distance effects and heavy degrees of freedom. We evaluate the chiral Lagrangian to order O(p{sup 4}) and to one loop to generate the dressing of the bare quark operators by pseudoscalar mesons. In addition we include the vector meson degrees of freedom in our study. Projection of the dressed quark operators on the baryonic level serves to calculate the relevant matrix elements. In a first application of this scheme, we resort to a parameterization of the valence quark form factors in the electromagnetic sector. Constraints
Quark contribution to the proton spin in the chiral quark-meson model
Energy Technology Data Exchange (ETDEWEB)
Stern, J. (Laboratoire de Physique Theorique, Universite des Sciences et de la Technologie Houari Boumediene, Alger (DZ)); Clement, G. (Departement de Physique, Ecole Normale Spuerieure, Vieux-Kouba, Alger (DZ))
1988-12-01
It has been argued that, to leading order in the 1/N/sub c/ expansion, very little of the spin of the proton is carried by the helicities of its constituent quarks, in accordance with the results of a recent EMC experiment. The authors investigate this question by a direct computation in the chiral quark-meson model, where the proton spin is generated by cranking a mean field hedgehog baryon. For not too small values of the quark-meson coupling constant, their results are consistent with the EMC data.
Chiral bags, skyrmions and quarks in nuclei
International Nuclear Information System (INIS)
Recent developments on an intriguing connection between the quark-bag description of the baryons (nucleons in particular) and the Skyrmion model are discussed in terms of the constraints coming from chiral anomalies. Topics treated are the leaking baryon charge, axial charge and energy density; the role of chiral anomalies; the role of Skyrme's quartic term and the connection to the meson degrees of freedom; and finally some qualitative implications in nuclei. The presentation is purposely descriptive and intuitive instead of mathematically precise
Two chiral nonet model with massless quarks
Fariborz, Amir H; Schechter, Joseph
2007-01-01
We present a detailed study of a linear sigma model containing one chiral nonet transforming under U(1)$_A$ as a quark-antiquark composite and another chiral nonet transforming as a diquark-anti diquark composite (or, equivalently from a symmetry point of view, as a two meson molecule). The model provides an intuitive explanation of a current puzzle in low energy QCD: Recent work has suggested the existence of a lighter than 1 GeV nonet of scalar mesons which behave like four quark composites. On the other hand, the validity of a spontaneously broken chiral symmetric description would suggest that these states be chiral partners of the light pseudoscalar mesons, which are two quark composites. The model solves the problem by starting with the two chiral nonets mentioned and allowing them to mix with each other. The input of physical masses in the SU(3) invariant limit for two scalar octets and an "excited" pion octet results in a mixing pattern wherein the light scalars have a large four quark content while t...
Chiral Lagrangians and quark condensate in nuclei
International Nuclear Information System (INIS)
The evolution of density of quark condensate in nuclear medium with interacting nucleons, including the short range correlations is examined. Two chiral models are used, the linear sigma model and the non-linear one. It is shown that the quark condensate, as other observables, is independent on the variant selected. The application to physical pions excludes the linear sigma model as a credible one. The non-linear models restricted to pure s-wave pion-nucleon scattering are examined. (author)
Constituent quark description of nucleon structure
International Nuclear Information System (INIS)
Nucleon structure functions are calculated within the constituent quark in the leading order. The results compare well with the experimental data for entire range of kinematics in x and Q2and with the next - to - leading order calculation of GRV
Decaying hadrons within constituent-quark models
Kleinhappel, Regina
2012-01-01
Within conventional constituent-quark models hadrons come out as stable bound states of the valence (anti)quarks. Thereby the resonance character of hadronic excitations is completely ignored. A more realistic description of hadron spectra can be achieved by including explicit mesonic degrees of freedom, which couple directly to the constituent quarks. We will present a coupled-channel formalism that describes such hybrid systems in a relativistically invariant way and allows for the decay of excited hadrons. The formalism is based on the point-form of relativistic quantum mechanics. If the confining forces between the (anti)quarks are described by instantaneous interactions it can be formally shown that the mass-eigenvalue problem for a system that consists of dynamical (anti)quarks and mesons reduces to a hadronic eigenvalue problem in which the eigenstates of the pure confinement problem (bare hadrons) are coupled via meson loops. The only point where the quark substructure enters are form factors at the m...
Masses of constituent quarks confined in open bottom hadrons
Jovanović, V Borka; Jovanović, P; Milošević, J; Ignjatović, S R
2014-01-01
We apply color-spin and flavor-spin quark-quark interactions to the meson and baryon constituent quarks, and calculate constituent quark masses, as well as the coupling constants of these interactions. The main goal of this manuscript was to determine constituent quark masses from light and open bottom hadron masses, using the fitting method we have developed and clustering of hadron groups. We use color-spin Fermi-Breit (FB) and flavor-spin Glozman-Riska (GR) hyperfine interaction (HFI) to determine constituent quark masses (especially $b$ quark mass). Our improved fitting procedure of constituent quark masses showed that both interactions we studied represent satisfactory approximations in the case of heavy mesons and baryons with $b$ quark, but on average color-spin (Fermi-Breit) hyperfine interaction yields better fits. Our method also shows the way how the constituent quark masses and the strength of the interaction constants appear in different hadron environments.
Chiral Lagrangian and chiral quark model from confinement in QCD
Simonov, Yu A
2015-01-01
The effective chiral Lagrangian in both nonlocal form $L_{ECCL}$ and standard local form $L_{ECL}$ are derived in QCD using the confining kernel, obtained in the vacuum correlator formalism. As a result all coefficients of $L_{ECL}$ can be computed via $q\\bar q$ Green's functions. In the $p^2$ order of $L_{ECL}$ one obtains GOR relations and quark decay constants $f_a$ are calculated $a=1,...8$, while in the $p^4$ order the coefficients $L_1, L_2, L_3,L_4, L_5, L_6$ are obtained in good agreement with the values given by data. The chiral quark model is shown to be a simple consequence of $L_{ECCL}$ with defined coefficients. It is demonstrated that $L_{ECCL}$ gives an extension of the limiting low-energy Lagrangian $L_{ECL}$ to arbitrary momenta.
Nucleon Properties from Approximating Chiral Quark Sigma Model
Abu-Shady, M
2009-01-01
We apply the approximating chiral quark model. This chiral quark model is based on an effective Lagrangian which the interactions between quarks via sigma and pions mesons. The field equations have been solved in the mean field approximation for the hedgehog baryon state. Good results are obtained for nucleon properties in comparison with original model.
Model for quark and lepton constituents
Energy Technology Data Exchange (ETDEWEB)
Fairlie, D.; Nuyts, J.; Taormina, A.
1983-01-01
A model of subconstituents for quarks and leptons is presented in which each of three different types transforms under a different group which is gauged. The binding is taken as magnetic, the dual of the usual electric charge and hence very strong. The spin of the constituents is zero. The spin of the bound states arises dynamically. Weak interactions violate parity maximally and the Weinberg angle, related to the generation problem, comes out well numerically. Two exotic states are predicted.
Model for quark and lepton constituents
Fairlie, D.; Nuyts, J.; Taormina, A.
1983-01-01
A model of subconstituents for quarks and leptons is presented in which each of three different types transforms under a different group which is gauged. The binding is taken as magnetic, the dual of the usual electric charge, and hence very strong. The spin of the constituents is zero. The spin of the bound states arises dynamically. Weak interactions violate parity maximally and the Weinberg angle, related to the generation problem, comes out well numerically. Two exotic states are predicted.
QCD phase transition with chiral quarks and physical quark masses.
Bhattacharya, Tanmoy; Buchoff, Michael I; Christ, Norman H; Ding, H-T; Gupta, Rajan; Jung, Chulwoo; Karsch, F; Lin, Zhongjie; Mawhinney, R D; McGlynn, Greg; Mukherjee, Swagato; Murphy, David; Petreczky, P; Renfrew, Dwight; Schroeder, Chris; Soltz, R A; Vranas, P M; Yin, Hantao
2014-08-22
We report on the first lattice calculation of the QCD phase transition using chiral fermions with physical quark masses. This calculation uses 2+1 quark flavors, spatial volumes between (4 fm)(3) and (11 fm)(3) and temperatures between 139 and 196 MeV. Each temperature is calculated at a single lattice spacing corresponding to a temporal Euclidean extent of N(t) = 8. The disconnected chiral susceptibility, χ(disc) shows a pronounced peak whose position and height depend sensitively on the quark mass. We find no metastability near the peak and a peak height which does not change when a 5 fm spatial extent is increased to 10 fm. Each result is strong evidence that the QCD "phase transition" is not first order but a continuous crossover for m(π) = 135 MeV. The peak location determines a pseudocritical temperature T(c) = 155(1)(8) MeV, in agreement with earlier staggered fermion results. However, the peak height is 50% greater than that suggested by previous staggered results. Chiral SU(2)(L) × SU(2)(R) symmetry is fully restored above 164 MeV, but anomalous U(1)(A) symmetry breaking is nonzero above T(c) and vanishes as T is increased to 196 MeV. PMID:25192088
N phi state in chiral quark model
Huang, F; Zhang, Z Y
2006-01-01
The structures of N phi states with spin-parity J^{p}=3/2^- and J^p=1/2^- are dynamically studied in both the chiral SU(3) quark model and the extended chiral SU(3) quark model by solving a resonating group method (RGM) equation. The model parameters are taken from our previous work, which gave a satisfactory description of the energies of the baryon ground states, the binding energy of the deuteron, the nucleon-nucleon (NN) scattering phase shifts, and the hyperon-nucleon (YN) cross sections. The channel coupling of N phi and Lambda K* is considered, and the effect of the tensor force which results in the mixing of S and D waves is also investigated. The results show that the N phi state has an attractive interaction, and in the extended chiral SU(3) quark model such an attraction plus the channel coupling effect can consequently make for an N phi quasi-bound state with several MeV binding energy.
Non-leptonic decays in an extended chiral quark model
Eeg, J O
2012-01-01
We consider the color suppressed (nonfactorizable) amplitude for the decay mode $\\bar{B_{d}^0} \\rightarrow \\pi^0 \\pi^{0} $. We treat the $b$-quark in the heavy quark limit and the energetic light ($u,d,s$) quarks within a variant of Large Energy Effective Theory combined with an extension of chiral quark models. Our calculated amplitude for $\\bar{B_{d}^0} \\rightarrow \\pi^0 \\pi^{0} $ is suppressed by a factor of order $\\Lambda_{QCD}/m_b$ with respect to the factorized amplitude, as it should according to QCD-factorization. Further, for reasonable values of the (model dependent) gluon condensate and the constituent quark mass, the calculated nonfactorizable amplitude for $\\bar{B_{d}^0} \\rightarrow \\pi^0 \\pi^{0} $ can easily accomodate the experimental value. Unfortunately, the color suppressed amplitude is very sensitive to the values of these model dependent parameters. Therefore fine-tuning is necessary in order to obtain an amplitude compatible with the experimental result for $\\bar{B_{d}^0} \\rightarrow \\pi^...
Current mass dependence of the quark condensate and the constituent quark mass
Musakhanov, M.
2001-01-01
We discuss the current mass dependence of the basic quantities of the quark models -- constituent quark mass M and quark condensate i. The framework of the consideration is QCD instanton vacuum model.
Dibaryons in a constituent quark model
Park, Woosung; Lee, Su Houng
2015-01-01
We investigate the properties of dibaryons containing u and d quarks in the constituent quark model. In constructing the ground state wave function, we choose the spatial part to be fully symmetric and the remaining color, isospin and spin part to be antisymmetric so as to satisfy the the Pauli principle. By adapting the IS coupling scheme that combine the isospin basis function with the spin basis function, and subsequently coupling this to the color singlet basis function, we construct the color $\\otimes$ isospin $\\otimes$ spin states compatible with the physical states of the dibaryon. By using the variational method, we then calculate the mass of the dibaryon in a nonrelativistic potential model, involving Coulomb, color confinement and color-spin hyperfine interaction. In particular, to asses the stability for different types of the confinement potential, we introduce one that is linearly proportional to the interquark distance and another to its square root. For all cases considered, we find that there ...
Nucleon structure functions from constituent quark
Khorramian, Ali N.; Arash, Firooz
1999-10-01
We have used a constituent quarks model to describe the nucleon structure function, F2( χ, Q2), for a wide range of χ=[10 -6,1] and Q2 = [0.5, 5000] GeV2. We have found that although F2 rises as χ decreases, but there exists some χ0 ≤ 10 -4 - 10 -5, below which the rise of F2 subsides drastically and hence, exhibits an almost flat behavior, compatible with the latest results from HERA, at least for low Q2.
Orbital Angular Momentum in the Chiral Quark Model
Song, Xiaotong
1998-01-01
We developed a new and unified scheme for describing both quark spin and orbital angular momenta in symmetry-breaking chiral quark model. The loss of quark spin in the chiral splitting processes is compensated by the gain of the orbital angular momentum carried by quarks and antiquarks. The sum of both spin and orbital angular momenta carried by quarks and antiquarks is 1/2. The analytic and numerical results for the spin and orbital angular momenta carried by quarks and antiquarks in the nuc...
Solitons in nonlocal chiral quark models
Broniowski, W; Ripka, G; Broniowski, Wojciech; Golli, Bojan; Ripka, Georges
2002-01-01
Properties of hedgehog solitons in a chiral quark model with nonlocal regulators are described. We discuss the formation of the hedgehog soliton, the quantization of the baryon number, the energetic stability, the gauging and construction of Noether currents with help of path-ordered P-exponents, and the evaluation of observables. The issue of nonlocality is thoroughly discussed, with a focus on contributions to observables related to the Noether currents. It is shown that with typical model parameters the solitons are not far from the weak nonlocality limit. The methods developed are applicable to solitons in models with separable nonlocal four-fermion interactions.
Constituent gluons and the static quark potential
Greensite, Jeff; Szczepaniak, Adam P.
2016-04-01
We suggest that Hamiltonian matrix elements between physical states in QCD might be approximated, in Coulomb gauge, by "lattice-improved" tree diagrams; i.e. tree diagram contributions with dressed ghost, transverse gluon, and Coulomb propagators obtained from lattice simulations. Such matrix elements can be applied to a truncated-basis treatment of hadronic states which include constituent gluons. As an illustration, we apply this hybrid approach to the heavy quark potential, for quark-antiquark separations up to 2.4 fm. The Coulomb string tension in SU(3) gauge theory is about a factor of 4 times greater than the asymptotic string tension. In our approach we show that a single constituent gluon is in principle sufficient, up to 2.4 fm, to reduce this overshoot by the factor required. The static potential remains linear, although the precise value of the string tension depends on details of the Couloumb gauge ghost and gluon propagators in the infrared regime. In this connection we present new lattice results for the transverse gluon propagator in position space.
The Quantum and Local Polyakov loop in Chiral Quark Models at Finite Temperature
Megias, E.; Arriola, E. Ruiz; Salcedo, L. L.
2006-01-01
We describe results for the confinement-deconfinement phase transition as predicted by the Nambu--Jona-Lasinio model where the local and quantum Polyakov loop is coupled to the constituent quarks in a minimal way (PNJL). We observe that the leading correlation of two Polyakov loops describes the chiral transition accurately. The effects of the current quark mass on the transition are also analysed.
Spin structure of constituent quark and polarized structure of hadrons
International Nuclear Information System (INIS)
Polarized parton distribution inside a constituent quark is calculated. This structure is universal for all hadrons and the polarized structure of any hadron is a convolution of polarized constituent quark distribution in the hadron with the polarized structure function of the constituent quark. This approach gives very good agreement with the experimental data on polarized proton, neutron, and deuteron. However, in order to assemble the components to build the spin the constituent quark we are forced to include a sizeable orbital angular momentum. (author)
Spin content of constituent quarks and one-spin asymmetries in inclusive processes
International Nuclear Information System (INIS)
A mechanism for one-spin asymmetries observed in inclusive hadron production is considered. The main role belongs to the orbital angular momentum of the quark-antiquark cloud in the internal structure of constituent quarks. The origin of the asymmetries in pion production is a result of retaining this internal angular orbital momentum by the perturbative phase of QCD under transition from the non-perturbative phase is proved. The non-perturbative hadron structure is based on the results of chiral quark models. 33 refs.; 8 figs
Strange quark matter in a chiral SU(3) quark mean field model
Wang, P.; Lyubovitskij, V. E.; Gutsche, Th.; Faessler, Amand
2002-01-01
We apply the chiral SU(3) quark mean field model to investigate strange quark matter. The stability of strange quark matter with different strangeness fraction is studied. The interaction between quarks and vector mesons destabilizes the strange quark matter. If the strength of the vector coupling is the same as in hadronic matter, strangelets can not be formed. For the case of beta equilibrium, there is no strange quark matter which can be stable against hadron emission even without vector m...
Quark matter inside neutron stars in an effective chiral model
International Nuclear Information System (INIS)
An effective chiral model which describes properties of a single baryon predicts that the quark matter relevant to neutron stars, close to the deconfinement density, is in a chirally broken phase. We find the SU(2) model that pion-condensed up and down quark matter is preferred energetically at neutron star densities. It exhibits spin ordering and can posses a permanent magnetization. The equation of state of quark matter with chiral condensate is very well approximated by bag model equation of the state with suitably chosen parameters. We study quark cores inside neutron stars in this model using realistic nucleon equations of state. The biggest quark core corresponds to the second order phase transition to quark matter. Magnetic moment of the pion-condensed quark core is calculated. (author). 19 refs, 10 refs, 1 tab
Explicit and Dynamical Chiral Symmetry Bresking in an Effective Quark-Quark Interaction Model
Institute of Scientific and Technical Information of China (English)
宗红石; 吴小华; 侯丰尧; 赵恩广
2004-01-01
A method for obtaining the small current quark mass effect on the dressed quark propagator from an effective quark-quark interaction model is developed. Within this approach both the explicit and dynamical chiral symmetry breakings are analysed. A comparison with the previous results is given.
NΩ and ΔΩ dibaryons in a SU(3) chiral quark model
International Nuclear Information System (INIS)
The binding energy of the six-quark system with strangeness s=-3 is investigated under the chiral SU(3) constituent quark model in the framework of RGM. The calculations of the single NΩ channel with spin S=2 and the single ΔΩ channel with spin S=3 are performed. The results show that both systems could be dibaryons and the interaction induced by the chiral field plays a very important role on forming bound states in the systems considered. The phase shifts and scattering lengths in corresponding channels are also given. (orig.)
LHCb pentaquarks in constituent quark models
Ortega, P G; Fernández, F
2016-01-01
The recently discovered $P_c(4380)^+$ and $P_c(4450)^+$ states at LHCb have masses close to the $\\bar D\\Sigma_c^*$ and $\\bar D^*\\Sigma_c$ thresholds, respectively, which suggest that they may have significant meson-baryon molecular components. We analyze these states in the framework of a constituent quark model which has been applied to a wide range of hadronic observables, being the model parameters, therefore, completely constrained. The $P_c(4380)^+$ and $P_c(4450)^+$ are studied as molecular states composed by charmed baryons and open charm mesons. Several bound states with the proper binding energy are found in the $\\bar D\\Sigma_c^*$ and $\\bar D^*\\Sigma_c$ channels. We discuss the possible assignments of these states from their decay widths. Moreover, two more states are predicted, associated with the $\\bar D\\Sigma_c$ and $\\bar D^* \\Sigma_c^*$ thresholds.
Constituent gluons and the static quark potential
Greensite, Jeff
2015-01-01
We suggest that Hamiltonian matrix elements between physical states in QCD might be approximated, in Coulomb gauge, by "lattice-improved" tree diagrams; i.e. tree diagram contributions with dressed ghost, transverse gluon, and Coulomb propagators obtained from lattice simulations. Such matrix elements can be applied to a variational treatment of hadronic states which include constituent gluons. As an illustration and first application of this hybrid approach, we derive a variational estimate of the heavy quark potential for distances up to 2.5 fm. The Coulomb string tension in SU(3) gauge theory is about a factor of four times greater than the asymptotic string tension. In our variational approach, using for simplicity a single variational parameter, we can reduce this overshoot by nearly the factor required. The building blocks of our approach are Coulomb gauge propagators, and in this connection we present new lattice results for the ghost and transverse gluon propagators in position space.
Constituent gluons and the static quark potential
Energy Technology Data Exchange (ETDEWEB)
Greensite, Jeff [San Francisco State Univ., CA (United States); Szczepaniak, Adam P. [Indiana Univ., Bloomington, IN (United States); Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
2016-04-01
We suggest that Hamiltonian matrix elements between physical states in QCD might be approximated, in Coulomb gauge, by "lattice-improved" tree diagrams; i.e. tree diagram contributions with dressed ghost, transverse gluon, and Coulomb propagators obtained from lattice simulations. Such matrix elements can be applied to a variational treatment of hadronic states which include constituent gluons. As an illustration and first application of this hybrid approach, we derive a variational estimate of the heavy quark potential for distances up to 2.5 fm. The Coulomb string tension in SU(3) gauge theory is about a factor of four times greater than the asymptotic string tension. In our variational approach, using for simplicity a single variational parameter, we can reduce this overshoot by nearly the factor required. The building blocks of our approach are Coulomb gauge propagators, and in this connection we present new lattice results for the ghost and transverse gluon propagators in position space.
Helicity-dependent generalized parton distributions and composite constituent quarks
Scopetta, S; Scopetta, Sergio; Vento, Vicente
2004-01-01
An approach recently proposed to calculate the nucleon generalized parton distributions (GPDs) in a constituent quark model (CQM) scenario, considering the constituent quarks as complex systems, is used here to obtain helicity-dependent GPDs. They are obtained from the wave functions of the non relativistic CQM of Isgur and Karl, convoluted with the helicity-dependent GPDs of the constituent quarks themselves. The latter are modelled by using the polarized structure functions of the constituent quark, the double distribution representation of GPDs, and a recently proposed phenomenological constituent quark form factor. The present approach permits to access a kinematical range corresponding to both the Dokshitzer-Gribov-Lipatov-Altarelli-Parisi and the Efremov-Radyushkin-Brodsky-Lepage regions, for small values of the momentum transfer and of the skewedness parameter. In this kinematical region, the present calculation represents a prerequisite for the evaluation of cross sections relevant to deeply virtual C...
Revisiting Chiral Extrapolation by Studying a Lattice Quark Propagator
Institute of Scientific and Technical Information of China (English)
ZHANG Yan-Bin; SUN Wei-Min; L(U) Xiao-Fu; ZONG Hong-Shi
2009-01-01
The quark propagator in the Landau gauge is studied on the lattice,including the quenched and the unquenched results.No obvious unquenched effects are found by comparing the quenched quark propagator with the dynamical one.For the quenched and unquenched configurations,the results with different quark masses have been computed.For the quark mass function,a nonlinear chiral extrapolating behavior is found in the in/tared region for both the quenched and dynamical results.
QQqq Four-Quark Bound States in Chiral SU(3) Quark Model
Institute of Scientific and Technical Information of China (English)
ZHANG Ming; ZHANG Hai-Xia; ZHANG Zong-Ye
2008-01-01
The possibility of QQqq heavy-light four-quark bound states has been analyzed by means of the chiral SU(3) quark model, where Q is the heavy quark (c or b) and q is the light quark (u, d, or s). We obtain a bound state for the bbnn configuration with quantum number JP=1+, I=0 and for the ccnn (JP=1+, I=0) configuration, which is not bound but slightly above the D*D* threshold (n is u or d quark). Meanwhile, we also conclude that a weakly bound state in bbnn system can also be found without considering the chiral quark interactions between the two light quarks, yet its binding energy is weaker than that with the chiral quark interactions.
Constituent-Quark Model and New Particles
Akers, D
2003-01-01
An elementary constituent-quark (CQ) model by Mac Gregor is reviewed with currently published data from light meson spectroscopy. It was previously shown in the CQ model that there existed several mass quanta m = 70 MeV, B = 140 MeV and X = 420 MeV, which were responsible for the quantization of meson yrast levels. The existence of a 70-MeV quantum was postulated by Mac Gregor and was shown to fit the Nambu empirical mass formula mn = (n/2)137me, n a positive integer. It is shown in this paper that recent data of new light mesons fit into the CQ model. With the introduction of the Russell-Saunders coupling scheme into the CQ model, several new meson particles are predicted to exist. The existence of the f0(560) meson is predicted and is shown to fit current experimental data from the Particle Data Group listing. The existence of meson partners or groupings is shown.
Hadron Structure Functions within a Chiral Quark Model
Weigel, H.(Physics Department, Stellenbosch University, Matieland 7602, South Africa); Gamberg, L.(Department of Physics, Penn State University-Berks, Reading, PA, 19610, U.S.A.)
2000-01-01
We outline a consistent regularization procedure to compute hadron structure functions within bosonized chiral quark models. We impose the Pauli--Villars scheme, which reproduces the chiral anomaly, to regularize the bosonized action. We derive the Compton amplitude from this action and utilize the Bjorken limit to extract structure functions that are consistent with the scaling laws and sum rules of deep inelastic scattering.
Nucleon and gamma N -> Delta lattice form factors in a constituent quark model
Ramalho, G
2008-01-01
A covariant quark model, based both on the spectator formalism and on Vector Meson Dominance, and previously calibrated by the physical data, is here extended to the unphysical region of the lattice data by means of one single extra adjustable parameter - the constituent quark mass in the chiral limit. We calculated the Nucleon (N) and the Gamma N -> Delta form factors in the universe of values for that parameter described by quenched lattice QCD. A qualitative description of the Nucleon and Gamma N -> Delta form factors lattice data is achieved for light pion masses.
Three-phase model of a chiral quark bag
International Nuclear Information System (INIS)
Three-phase modification of the model of hybrid chiral quark bag is suggested. Along with the phase of asymptotically free current quarks and completely achromatic meson phase the model contains an intermediate phase including massive quark components. Self-consistent solution of model equations with account of contribution from the Dirac sea is found for (1+1)-dimensional case. The dependence of bag characteristics on theory parameters is investigated in analytical and numerical forms
Adler function and hadronic contribution to the muon g-2 in a nonlocal chiral quark model
International Nuclear Information System (INIS)
The behavior of the vector Adler function at spacelike momenta is studied in the framework of a covariant chiral quark model with instantonlike quark-quark interaction. This function describes the transition between the high-energy asymptotically free region of almost massless current quarks to the low-energy hadronized regime with massive constituent quarks. The model reproduces the Adler function and V-A correlator extracted from the ALEPH and OPAL data on hadronic τ lepton decays, transformed into the Euclidean domain via dispersion relations. The leading order contribution from the hadronic part of the photon vacuum polarization to the anomalous magnetic moment of the muon, aμhvp(1), is estimated
On Possible S-Wave Bound States for an N-(N) System Within a Constituent Quark Model
Institute of Scientific and Technical Information of China (English)
CHANG Chao-Hsi; PANG Hou-Rong
2005-01-01
We try to apply a constituent quark model (a variety chiral constituent quark model) and the resonating group approach for the multi-quark problems to compute the effective potential between the NN- in S-wave (the quarks in the nucleons N and N-, and the two nucleons relatively as well, are in S wave) so as to see the possibility if there may be a tight bound state of six quarks as indicated by a strong enhancement at threshold of pp- in J/ψ and B decays. The effective potential which we obtain in terms of the model and approach shows if the experimental enhancement is really caused by a tight S-wave bound state of six quarks, then the quantum number of the bound state is very likely to be I = 1, JPC= 0-+.
ΞΩ and Ξ*Ω dibaryons in SU(3) chiral quark model
International Nuclear Information System (INIS)
The binding energy of the six quark system with strangeness s = -5 is investigated by the SU(3) chiral constituent quark model. the single Ξ*Ω channel calculation with spin S = 0 and the coupled ΞΩ-Ξ*Ω channel calculation with spin S = 1 are considered. It is shown that in the spin S = 0 case, the binding energy of Ξ*Ω is ranged from 80.0 to 92.4 MeV, while in the S = 1 case, the additional Ξ*Ω channel increases the binding energy of ΞΩ to a range of 26.2-32.9 MeV
Chiral phase transition scenarios from the vector meson extended Polyakov quark meson model
Kovács, Péter
2015-01-01
Chiral phase transition is investigated in an $SU(3)_L \\times SU(3)_R$ symmetric vector meson extended linear sigma model with additional constituent quarks and Polyakov loops (extended Polyakov quark meson model). The parameterization of the Lagrangian is done at zero temperature in a hybrid approach, where the mesons are treated at tree-level, while the constituent quarks at 1-loop level. The temperature and baryochemical potential dependence of the two assumed scalar condensates are calculated from the hybrid 1-loop level equations of states. The order of the phase transition along the $T=0$ and $\\mu_B=0$ axes are determined for various parameterization scenarios. We find that in order to have a first order phase transition at $T=0$ as a function of $\\mu_B$ a light isoscalar particle is needed.
Ω(ε)States in a Chiral Quark Model
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
The structures of Ω(ε) states with spin-parity Jp = 5/2-, 3/2-, and 1/2- are dynamically studied in both the chiral SU(3) quark model and the extended chiral SU(3) quark model by solving a resonating group method (RGM) equation. The model parameters are taken from our previous work, which gave a satisfactory description of the energies of the baryon ground states, the binding energy of the deuteron, the nucleon-nucleon (NN) scattering phase shifts, and the hyperon-nucleon (YN) cross sections. The calculated results show that theΩ(ε) state has an attractive interaction, and in the extended chiral SU(3) quark model such attraction can make for aΩ(ε) quasi-bound state with spin-parity Jp = 3/2- or 5/2- and tie binding energy of about several MeV.
Proton parton-distribution functions from the nonlocal Chiral-Quark model
International Nuclear Information System (INIS)
Full text: We investigate the parton distribution functions for the proton, employing the gauge invariant nonlocal chiral-quark model. By the virtue of the Drell-Yan-Levy relation, we compute the parton distribution and fragmentation (splitting) functions for the pion and kaon consistently within the present model at the low renormalization scale ∼1 GeV which are necessary for computing the fluctuations of the quarks inside the proton. All the model parameters are determined by the normalization condition for the parton distribution functions and the empirical data for the weak-decay constants for the pion and kaon. As for the initial constituent quark, we use a simple Gaussian-type distribution, developed at the nucleon rest frame. All the results are evolved to high-Q2 via the DGLAP equations, then compared with presently available experimental data. We also discuss the asymmetry for the sea-quark distributions in the proton.
Meson phenomenology and phase transitions in nonlocal chiral quark models
Carlomagno, J. P.; Gomez Dumm, D.; Pagura, V.; Scoccola, N. N.
2015-07-01
We study the features of nonlocal chiral quark models that include wave function renormalization. Model parameters are determined from meson phenomenology, considering different nonlocal form factor shapes. In this context we analyze the characteristics of the deconfinement and chiral restoration transitions at finite temperature and chemical potential, introducing the couplings of fermions to the Polyakov loop for different Polyakov potentials. The results for various thermodynamical quantities are compared with data obtained from lattice QCD calculations.
Vacuum quark condensate, chiral Lagrangian, and Bose-Einstein statistics
International Nuclear Information System (INIS)
In a series of articles it was recently claimed that the quantum chromodynamic (QCD) condensates are not the properties of the vacuum but of the hadrons and are confined inside them. We point out that this claim is incompatible with the chiral Lagrangian and Bose-Einstein statistics of the Goldstone bosons (pions) in chiral limit and conclude that the quark condensate must be the property of the QCD vacuum.
Chiral Transition Within Effective Quark Models under Strong Magnetic Fields
Garcia, Andre Felipe
2013-01-01
In the recently years it has been argued that spectators in heavy ion collisions are responsible for creating a strong magnetic field that could play an important role in the QCD phase transition. In this work we use the SU(2) Nambu--Jona-Lasinio (NJL) model in order to study the chiral transition in quark matter subject to a strong magnetic field. We show some results involving the breaking of chiral symmetry and its restoration at finite temperature and density.
Chiral Quark Meson Theory for N and Δ
International Nuclear Information System (INIS)
The Chiral Quark Meson Theory (CQMT) is a theory of effective interaction designed to describe the action of quantum chromodynamics in the ground state of the nucleon (N) and delta (Δ). It is conjectured that N and Δ are describable satisfactorily in terms of independently moving quarks. The quark wave function is restricted to be a single determinant. This precludes the possibility of describing a single nucleon. The theory must deal with a linear combination of N and Δ. The role of octet gluon towers was examined, with the finding that it can be simulated at the mean field level by a chiral invariant quark-meson lagrangian. Various nucleon properties were calculated. 24 refs., 5 figs., 2 tabs
Stable $uuddbar s$ pentaquarks in the constituent quark model
Stancu, F; Stancu, Fl.
2003-01-01
The stability of strange pentaquarks $uuddbar s$ is studied in a constituent quark model based on a flavor-spin hyperfine interaction between quarks. With this interaction model, which schematically represents the Goldstone boson exchange interaction between constituent quarks, the lowest lying strange pentaquark is a $p-$shell state with positive parity. The flavor-spin interaction lowers the energy of the lowest $p-$shell state below that of the lowest $s-$shell state, which has negative parity because of the negative parity of the strange antiquark. It is found that the strange pentaquark is stable against strong decay provided that the strange antiquark interacts by a fairly strong spin-spin interaction with $u$ and $d$ quarks. This interaction has a form that corresponds to $eta$ meson exchange. Its strength may be inferred from the $pi^0$ decay width of $D_s^*$ mesons.
A Euclidean bridge to the relativistic constituent quark model
Hobbs, T J; Miller, Gerald A
2016-01-01
${\\bf Background}$ Knowledge of nucleon structure is today ever more of a precision science, with heightened theoretical and experimental activity expected in coming years. At the same time, a persistent gap lingers between theoretical approaches grounded in Euclidean methods (e.g., lattice QCD, Dyson-Schwinger Equations [DSEs]) as opposed to traditional Minkowski field theories (such as light-front constituent quark models). ${\\bf Purpose}$ Seeking to bridge these complementary worldviews, we explore the potential of a Euclidean constituent quark model (ECQM). This formalism enables us to study the gluonic dressing of the quark-level axial-vector vertex, which we undertake as a test of the framework. ${\\bf Method}$ To access its indispensable elements with a minimum of inessential detail, we develop our ECQM using the simplified quark $+$ scalar diquark picture of the nucleon. We construct a hyperspherical formalism involving polynomial expansions of diquark propagators to marry our ECQM with the results of ...
ND^(*) and NB^(*) interactions in a chiral quark model
Yang, Dan; Zhang, Dan
2015-01-01
ND and ND^* interactions become a hot topic after the observation of new charmed hadrons \\Sigma_c(2800) and \\Lambda_c(2940)^+. In this letter, we have preliminary investigated S-wave ND and ND^* interactions with possible quantum numbers in the chiral SU(3) quark model and the extended chiral SU(3) quark model by solving the resonating group method equation. The numerical results show that the interactions between N and D or N and D^* are both attractive, which are mainly from \\sigma exchanges between light quarks. Further bound-state studies indicate the attractions are strong enough to form ND or ND^* molecules, except for (ND)_{J=3/2} and (ND^*)_{J=3/2} in the chiral SU(3) quark model. In consequence ND system with J=1/2 and ND^* system with J=3/2 in the extended SU(3) quark model could correspond to the observed \\Sigma_c(2800) and \\Lambda_c(2940)^+, respectively. Naturally, the same method can be applied to research NB and NB^* interactions, and similar conclusions obtained, i.e. NB and NB^* attractive fo...
Hadron Properties in a Chiral Quark-Sigma Model
Rashdan, M; El-Kholy, S; Abu-Shady, M
2011-01-01
Within a chiral quark sigma model in which quarks interact via the exchange of sigma and pi-mesons, hadron properties are investigated. This model of the nucleon and delta is based on the idea that strong QCD forces on very short distances (a small length scales 0.2- 1 fm) result in hidden chiral SU(2)xSU(2) symmetry and that there is a separation of roles between these forces which are responsible for binding quarks in hadrons and the forces which produce absolute confinement. We have solved the field equations in the mean field approximation for the hedgehog baryon state with different sets of model parameters. A new parametrization which well describe the nucleon properties has been introduced and compared with experimental data.
Tensor Susceptibilities of the Vacuum from Constituent Quarks
International Nuclear Information System (INIS)
We show that the constituent quark model leads to simple expression for the isoscalar and isovector tensor susceptibilities of the vacuum. The found values are negative and of magnitude compatible with QCD-sum-rule parametrizations of spectral densities in appropriate L=1-meson channels. (author)
Influence of the Polyakov loop on the chiral phase transition in the two flavor chiral quark model
Markó, G.; Szép, Zs.
2010-09-01
The SU(2)L×SU(2)R chiral quark model consisting of the (σ,π→) meson multiplet and the constituent quarks propagating on the homogeneous background of a temporal gauge field is solved at finite temperature and quark baryon chemical potential μq using an expansion in the number of flavors Nf, both in the chiral limit and for the physical value of the pion mass. Keeping the fermion propagator at its tree level, several approximations to the pion propagator are investigated. These approximations correspond to different partial resummations of the perturbative series. Comparing their solution with a diagrammatically formulated resummation relying on a strict large-Nf expansion of the perturbative series, one concludes that only when the local part of the approximated pion propagator resums infinitely many orders in 1/Nf of fermionic contributions a sufficiently rapid crossover transition at μq=0 is achieved allowing for the existence of a tricritical point or a critical end point in the μq-T phase diagram. The renormalization and the possibility of determining the counterterms in the resummation provided by a strict large-Nf expansion are investigated.
Transversity structure of the pion in chiral quark models
Broniowski, Wojciech; Dorokhov, Alexander E
2011-01-01
We describe the chiral quark model evaluation of the transversity Generalized Parton Distributions (tGPDs) and related transversity form factors (tFFs) of the pion. The obtained tGPDs satisfy all necessary formal requirements, such as the proper support, normalization, and polynomiality. The lowest tFFs, after the necessary QCD evolution, compare favorably to the recent lattice QCD determination. Thus the transversity observables of the pion support once again the fact that the spontaneously broken chiral symmetry governs the structure of the Goldstone pion. The proper QCD evolution is crucial in these studies.
Chiral Lagrangian with Heavy Quark-Diquark Symmetry
Energy Technology Data Exchange (ETDEWEB)
Jie Hu; Thomas Mehen
2005-11-29
We construct a chiral Lagrangian for doubly heavy baryons and heavy mesons that is invariant under heavy quark-diquark symmetry at leading order and includes the leading O(1/m{sub Q}) symmetry violating operators. The theory is used to predict the electromagnetic decay width of the J=3/2 member of the ground state doubly heavy baryon doublet. Numerical estimates are provided for doubly charm baryons. We also calculate chiral corrections to doubly heavy baryon masses and strong decay widths of low lying excited doubly heavy baryons.
A Review of Heavy-Quark and Chiral Perturbation Theory
Naboulsi, R
2003-01-01
In this paper we discuss the relations between various decays that can be obtained by combining heavy-quark perturbation theory and chiral perturbation theory for the emission of soft pseudoscalar particles. In the heavy-quark limit of QCD the interactions of the heavy quark Q are simplified because of a new set of symmetries not manifestly present in the full QCD. This fact is usually used in the construction of the new effective theory where the heavy-quark mass goes to infinity $(m_Q\\gg \\Lambda_{QCD})$ with its four-velocity fixed. The spin-flavor symmetry group of this new theory with N heavy quarks is SU(2N) because the interactions of the heavy quarks are independent of their spins and flavors. This fact is widely used in the description of the semileptonic decays of $B$ mesons to $D$ and $D^\\ast$ mesons where heavy-quark symmetry allows a parameterization of the decay amplitudes in terms of the single Isgur-Wise function [1].
Scalar mesons in a chiral quark model with glueball
International Nuclear Information System (INIS)
Ground-state scalar isoscalar mesons and a scalar glueball are described in a U(3)xU(3) chiral quark model of the Nambu-Jona-Lasinio (NJL) type with 't Hooft interaction. The latter interaction produces singlet-octet mixing in the scalar and pseudoscalar sectors. The glueball is introduced into the effective meson Lagrangian as a dilaton on the basis of scale invariance. The mixing of the glueball with scalar isoscalar quarkonia and amplitudes of their decays into two pseudoscalar mesons are shown to be proportional to current quark masses, vanishing in the chiral limit. Mass spectra of the scalar mesons and the glueball and their main modes of strong decay are described
Soft Matrix Elements in Non-local Chiral Quark Model
Kotko, Piotr
2009-01-01
Using non-local chiral quark model and currents satisfying Ward-Takahashi identities we analyze Distribution Amplitudes (DA) of photon and pion-to-photon Transition Distribution Amplitudes (TDA) in the low energy regime. Photon DA's are calculated analytically up to twist-4 and reveal several interesting features of photon structure. TDA's calculated in the present model satisfy polynomiality condition. Normalization of vector TDA is fixed by the axial anomaly. We also compute relevant form f...
Spontaneous magnetization of quark matter in the inhomogeneous chiral phase
Yoshiike, Ryo; Tatsumi, Tositaka
2015-01-01
Considering the density wave of scalar and pseudoscalar condensates, we study the response of quark matter to a weak external magnetic field. In an external magnetic field, the energy spectrum of the lowest Landau level becomes asymmetric about zero, which is closely related to chiral anomaly, and gives rise to the spontaneous magnetization. This mechanism may be one of candidates for the origin of the strong magnetic field in pulsars and/or magnetars.
The QCD phase transition with physical-mass, chiral quarks
Bhattacharya, Tanmoy; Christ, Norman H; Ding, H -T; Gupta, Rajan; Jung, Chulwoo; Karsch, F; Lin, Zhongjie; Mawhinney, R D; McGlynn, Greg; Mukherjee, Swagato; Murphy, David; Petreczky, P; Schroeder, Chris; Soltz, R A; Vranas, P M; Yin, Hantao
2014-01-01
We report on the first lattice calculation of the QCD phase transition using chiral fermions at physical values of the quark masses. This calculation uses 2+1 quark flavors, spatial volumes between (4 fm$)^3$ and (11 fm$)^3$ and temperatures between 139 and 196 MeV . Each temperature was calculated using a single lattice spacing corresponding to a temporal Euclidean extent of $N_t=8$. The disconnected chiral susceptibility, $\\chi_{\\rm disc}$ shows a pronounced peak whose position and height depend sensitively on the quark mass. We find no metastability in the region of the peak and a peak height which does not change when a 5 fm spatial extent is increased to 10 fm. Each result is strong evidence that the QCD ``phase transition'' is not first order but a continuous cross-over for $m_\\pi=135$ MeV. The peak location determines a pseudo-critical temperature $T_c = 155(1)(8)$ MeV. Chiral $SU(2)_L\\times SU(2)_R$ symmetry is fully restored above 164 MeV, but anomalous $U(1)_A$ symmetry breaking is non-zero above $T...
Ilichova, T. P.
2002-01-01
A nonrelativistic decomposition for the quark energy by the ratio of the dispersion of quark momentum squared and the effective quark mass is investigated in the framework of the relativistic oscillator constituent quark model as bound systems of three valence quarks. It is shown that relativistic corrections are defined by dispersion of the squared absolute value of the quark momentum. The variations of the quark mass and oscillator parameter are studied in detail both in the spectrum and in...
Constituent quark scaling violation due to baryon number transport
Dunlop, J; Sorensen, P
2011-01-01
In ultra-relativistic heavy ion collisions at $\\roots\\approx200$ GeV, the azimuthal emission anisotropy of hadrons with low and intermediate transverse momentum ($p_T\\lesssim 4$ GeV/c) displays an intriguing scaling. In particular, the baryon (meson) emission patterns are consistent with a scenario in which a bulk medium of flowing quarks coalesces into three-quark (two-quark) "bags." While a full understanding of this number of constituent quark (NCQ) scaling remains elusive, it is suggestive of a thermalized bulk system characterized by colored dynamical degrees of freedom-- a quark-gluon plasma (QGP). In this scenario, one expects the scaling to break down as the central energy density is reduced below the QGP formation threshold; for this reason, NCQ-scaling violation searches are of interest in the energy scan program at the Relativistic Heavy Ion Collider (RHIC). However, as $\\roots$ is reduced, it is not only the initial energy density that changes; there is also an increase in the net baryon number at...
Chiral superfluidity of the quark-gluon plasma
Energy Technology Data Exchange (ETDEWEB)
Kalaydzhyan, Tigran [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Institute for Theoretical and Experimental Physics ITEP, Moscow (Russian Federation)
2012-08-15
In this paper we argue that the strongly coupled quark-gluon plasma can be considered as a chiral superfluid. The ''normal'' component of the fluid is the thermalized matter in common sense, while the ''superfluid'' part consists of long wavelength (chiral) fermionic states moving independently. We use several nonperturbative techniques to demonstrate that. First, we analyze the fermionic spectrum in the deconfinement phase (T{sub c}
Higher twists in polarized DIS and the size of the constituent quark
Energy Technology Data Exchange (ETDEWEB)
Alexander Sidorov; Christian Weiss
2006-02-15
The spontaneous breaking of chiral symmetry implies the presence of a short-distance scale in the QCD vacuum, which phenomenologically may be associated with the ''size'' of the constituent quark, rho {approx} 0.3 fm. We discuss the role of this scale in the matrix elements of the twist-4 and 3 quark-gluon operators determining the leading power (1/Q{sup 2}-) corrections to the moments of the nucleon spin structure functions. We argue that the flavor-nonsinglet twist-4 matrix element, f{sub 2}{sup u-d}, has a sizable negative value of the order rho{sup -2}, due to the presence of sea quarks with virtualities {approx} rho{sup -2} in the proton wave function. The twist-3 matrix element, d{sub 2}, is not related to the scale rho{sup -2}. Our arguments support the results of previous calculations of the matrix elements in the instanton vacuum model. We show that this qualitative picture is in agreement with the phenomenological higher-twist correction extracted from an NLO QCD fit to the world data on g{sub 1}{sup p} and g{sub 1}{sup n}, which include recent data from the Jefferson Lab Hall A and COMPASS experiments. We comment on the implications of the short-distance scale rho for quark-hadron duality and the x-dependence of higher-twist contributions.
Dibaryons with two strange quarks and one heavy flavor in a constituent quark model
Park, Aaron; Lee, Su Houng
2016-01-01
We investigate the symmetry property and the stability of dibaryons containing two strange quarks and one heavy flavor with $I=\\frac{1}{2}$. We construct the wave function of the dibaryon in two ways. First, we directly construct the color and spin state of the dibaryon starting from the four possible SU(3) flavor state. Second, we consider the states composed of five light quarks, and then construct the wave function of the dibaryon by adding one heavy quark. The stability of the dibaryon against the strong decay into two baryons is discussed by using variational method in a constituent quark model with confining and hyperfine potential. We find that for all configurations with S=0,1,2, the ground states of the dibaryons are the sum of two baryons, and there are no compact bound state that is stable against the strong decay.
The chiral phase transition for QCD with sextet quarks
Sinclair, D K
2011-01-01
QCD with 2 massless colour-sextet quarks is studied as a model of Walking Technicolor. We simulate lattice QCD with 2 light color-sextet staggered quarks at finite temperature, and use the dependence of the coupling at the chiral transition on the temporal extent, $N_t$, of the lattice in lattice units to study the running of the bare lattice coupling with lattice spacing. Our goal is to determine whether this theory is QCD-like and `walks', or if it is conformal. If it is QCD-like, the coupling at the chiral transition should tend to zero as $N_t \\rightarrow \\infty$ in a manner controlled by asymptotic freedom, i.e. by the perturbative $\\beta$-function. On the other hand, if this theory is conformal, this coupling will approach a non-zero limit in the $N_t \\rightarrow \\infty$ limit. We are extending our simulations on an $N_t=8$ lattice to determine the position of the chiral transition with greater accuracy, and are performing simulations on an $N_t=12$ lattice.
A Constituent Quark-Meson Model for Heavy Meson Decays
Deandrea, Aldo
1998-01-01
I describe a model for heavy meson decays based on an effective quark-meson lagrangian. I consider the heavy mesons S with spin and parity J^P=(1+,0+), H with J^P=(1-,0-) and T^mu with J^P=(2+,1+), i.e. S and P wave heavy-light mesons. The model is constrained by the known symmetries of QCD in the mQ -> infinity limit for the heavy quarks, and chiral symmetry in the light quark sector. Using a very limited number of free parameters it is possible to compute several phenomenological quantities, e.g. the leptonic B and B** decay constants; the three universal Isgur-Wise form factors: xi, tau(3/2), tau(1/2), describing the semi-leptonic decays B -> D(*) l nu, B -> D** l nu; the strong and radiative D* decays; the weak semi-leptonic decays of B and D into light mesons: pi, rho, a1. An overall agreement with data, when available, is achieved.
Chiral Quark Soliton Model and Nucleon Spin Structure Functions
Wakamatsu, M
2009-01-01
The chiral quark soliton model (CQSM) is one of the most successful models of baryons at quark level, which maximally incorporates the most important feature of low energy QCD, i.e. the chiral symmetry and its spontaneous breakdown. Basically, it is a relativistic mean-field theory with full account of infinitely many Dirac-sea quarks in a rotational-symmetry-breaking mean field of hedgehog shape. The numerical technique established so far enables us to make a nonperturbative evaluation of Casimir effects (i.e. effects of vacuum-polarized Dirac sea) on a variety of baryon observables. This incompatible feature of the model manifests most clearly in its predictions for parton distribution functions of the nucleon. In this talk, after briefly reviewing several basic features of the CQSM, we plan to demonstrate in various ways that this unique model of baryons provides us with an ideal tool for disentangling nonperturbative aspect of the internal partonic structure of the nucleon, especially the underlying spin ...
Various decays of some hadronic systems in constituent quark models
International Nuclear Information System (INIS)
The topic of this study is the decay of mesons in constituent quark models. Those models as well as the various quark-antiquark interaction potentials are presented. Strong decay of a meson into two or three mesons is studied in the second part. The original 3Po model is presented as well as the research of a vertex function γ(p) depending on the momentum for the created qq-bar pair. We show that a function γ(p) of constant+Gaussian type is superior than the constant usually used. The second part is dedicated to electromagnetic transitions studied through the emission of a real or a virtual photon. In the case of real photon emission, the different approximations found in the literature are reviewed and compared to the formalism going beyond the long wave length approximation. Mixing angles are tested for some mesons. In the case of virtual photon, the expression of decay width obtained by van Royen and Weisskopf is re-demonstrated and then improved by taking into account the quark momentum distribution inside the meson. An electromagnetic dressing of quarks is introduced that improves the results. All along this study, wave functions of various sophistication degrees are used. The results of decay widths are compared to a large bulk of experimental data. (author)
Effective meson lagrangian with chiral and heavy quark symmetries from quark flavor dynamics
International Nuclear Information System (INIS)
By bosonization of an extended NJL model we derive an effective meson theory which describes the interplay between chiral symmetry and heavy quark dynamics. This effective theory is worked out in the low-energy regime using the gradient expansion. The resulting effective lagrangian describes strong and weak interactions of heavy B and D mesons with pseudoscalar Goldstone bosons and light vector and axial-vector mesons. Heavy meson weak decay constants, coupling constants and the Isgur-Wise function are predicted in terms of the model parameters partially fixed from the light quark sector. Explicit SU(3)F symmetry breaking effects are estimated and, if possible, confronted with experiment. ((orig.))
Proton Spin Based On Chiral Dynamics
Weber, H. J.
1999-01-01
Chiral spin fraction models agree with the proton spin data only when the chiral quark-Goldstone boson couplings are pure spinflip. For axial-vector coupling from soft-pion physics this is true for massless quarks but not for constituent quarks. Axial-vector quark-Goldstone boson couplings with {\\bf constituent} quarks are found to be inconsistent with the proton spin data.
Inclusive resonance spectra, constituent quark distributions and dual topological Pomeron
International Nuclear Information System (INIS)
Inclusive vector meson spectra from soft hadron-hadron collisions are given in the framework of the dual topological unitarization scheme, into which constituent quark (or valon) distributions inside initial hadrons are incorporated. Dual topological Pomeron corresponds to multiple production of clusters, each of which is assumed to be composed of a vector, tensor and pseudoscalar mesons. The pion and kaon spectra in the fragmentation region are saturated by the cluster model, but those in the central region indicate that we further need higher resonances decaying into more pions and kaons than vector and tensor mesons. (author)
Soft Matrix Elements in Non-local Chiral Quark Model
Kotko, Piotr
2009-01-01
Using non-local chiral quark model and currents satisfying Ward-Takahashi identities we analyze Distribution Amplitudes (DA) of photon and pion-to-photon Transition Distribution Amplitudes (TDA) in the low energy regime. Photon DA's are calculated analytically up to twist-4 and reveal several interesting features of photon structure. TDA's calculated in the present model satisfy polynomiality condition. Normalization of vector TDA is fixed by the axial anomaly. We also compute relevant form factors and compare them with existing data. Axial form factor turns out to be much lower then the vector one, what indeed is seen in the experimental data.
Spontaneous Magnetization of Quark Matter in Inhomogeneous Chiral Phase
Yoshiike, Ryo; Tatsumi, Toshitaka
2015-01-01
Considering the density wave of scalar and pseudoscalar condensates, we study the response of quark matter to a weak external magnetic field. In an external magnetic field, the energy spectrum of the lowest Landau level becomes asymmetric about zero, which is closely related to chiral anomaly. This spectral asymmetry gives rise to spontaneous magnetization. This mechanism may be one of candidates for the origin of the strong magnetic field in magnetars. Furthermore, using the generalized Ginzburg-Landau(gGL) expansion, we show that magnetic susceptibility exhibits a peculiar feature
Sea quark transverse momentum distributions and dynamical chiral symmetry breaking
Energy Technology Data Exchange (ETDEWEB)
Schweitzer, Peter [Univ. of Connecticut, Storrs, CT (United States); Strikman, Mark [Penn State Univ., State College, PA (United States); Weiss, Christian [JLAB Newport News, VA (United States)
2014-01-01
Recent theoretical studies have provided new insight into the intrinsic transverse momentum distributions of valence and sea quarks in the nucleon at a low scale. The valence quark transverse momentum distributions (q - qbar) are governed by the nucleon's inverse hadronic size R{sup -1} ~ 0.2 GeV and drop steeply at large p{sub T}. The sea quark distributions (qbar) are in large part generated by non-perturbative chiral-symmetry breaking interactions and extend up to the scale rho{sup -1} ~ 0.6 GeV. These findings have many implications for modeling the initial conditions of perturbative QCD evolution of TMD distributions (starting scale, shape of p{sub T}. distributions, coordinate-space correlation functions). The qualitative difference between valence and sea quark intrinsic p{sub T}. distributions could be observed experimentally, by comparing the transverse momentum distributions of selected hadrons in semi-inclusive deep-inelastic scattering, or those of dileptons produced in pp and pbar-p scattering.
Asymmetries of quark sea in nucleon
Dahiya Harleen
2014-01-01
The effects of “quark sea” in determining the flavor structure of the octet baryons have been investigated in the chiral constituent quark model. The chiral constituent quark model is able to qualitatively generate the requisite amount of quark sea and is also known to provide a satisfactory explanation of the proton spin and related issues in the nonperturbative regime. The phenomenological implications of the quark sea asymmetries in the nucleon have been investigated to understand the impo...
Negative-parity hyperons in the constituent quark model with meson-quark couplings
International Nuclear Information System (INIS)
Negative-parity hyperons are systematically studied by means of the constituent quark model which incorporates the effect of the meson-quark coupling. Some unresolved puzzles of these resonances are investigated; the mass splitting between Λ(1405) and Λ(1520) can be realized by the difference of their self-energies due to the mesonic effect, without losing the general success of the constituent quark model; the couplings of the so-called ''missing resonances'' to the meson-baryon states are shown to be suppressed owing to the spin-flavor symmetry of the quark wave functions of the resonances. Although only the resonance contribution is considered for the meson-baryon scattering, the calculated amplitudes have the energy dependence consistent with the phase-shift analyses of the data. To obtain more quantitative agreement, however, the improvement of the model will be necessary; for example, non-resonant contribution is required to explain the isovector KN amplitude at low energies. (orig.)
charmed baryon strong decays in a chiral quark model
Zhong, Xian-Hui
2007-01-01
Charmed baryon strong decays are studied in a chiral quark model. The data for the decays of $\\Lambda^+_c(2593)$, $\\Lambda^+_c(2625)$, $\\Sigma^{++,+,0}_c$ and $\\Sigma^{+,0}_c(2520)$, are accounted for successfully, which allows to fix the pseudoscalar-meson-quark couplings in an effective chiral Lagrangian. Extending this framework to analyze the strong decays of the newly observed charmed baryons, we classify that both $\\Lambda_c(2880)$ and $\\Lambda_c(2940)$ are $D$-wave states in the N=2 shell; $\\Lambda_c(2880)$ could be $|\\Lambda_c ^2 D_{\\lambda\\lambda}{3/2}^+>$ and $\\Lambda_c(2940)$ could be $|\\Lambda_c ^2 D_{\\lambda\\lambda}{5/2}^+>$. Our calculation also suggests that $\\Lambda_c(2765)$ is very likely a $\\rho$-mode $P$-wave excited state in the N=1 shell, and favors a $|\\Lambda_c ^4P_\\rho 1/2^->$ configuration. The $\\Sigma_c(2800)$ favors being a $|\\Sigma_c ^2P_\\lambda{1/2}^->$ state. But its being $|\\Sigma^{++}_c ^4 P_\\lambda{5/2}^->$ cannot be ruled out.
Finite-temperature corrections in the dilated chiral quark model
International Nuclear Information System (INIS)
We calculate the finite-temperature corrections in the dilated chiral quark model using the effective potential formalism. Assuming that the dilaton limit is applicable at some short length scale, we interpret the results to represent the behavior of hadrons in dense and hot matter. We obtain the scaling law, fπ(T)/fπ = mQ(T)/mQ ≅ mσ(T)/mσwhile we argue, using PCAC, that pion mass does not scale within the temperature range involved in our Lagrangian. It is found that the hadron masses and the pion decay constant drop faster with temperature in the dilated chiral quark model than in the conventional linear sigma model that does not take into account the QCD scale anomaly. We attribute the difference in scaling in heat bath to the effect of baryonic medium on thermal properties of the hadrons. Our finding would imply that the AGS experiments (dense and hot matter) and the RHIC experiments (hot and dilute matter) will ''see'' different hadron properties in the hadronization exit phase
Dibaryons with two strange quarks and total spin zero in a constituent quark model
Park, Woosung; Park, Aaron; Lee, Su Houng
2016-04-01
We investigate the symmetry property and construct the wave function of the dibaryon states containing two strange quarks with S =0 in both the flavor SU(3) symmetric and breaking cases. We discuss how the color ⊗ isospin ⊗ spin states of dibaryon in the symmetry broken case of flavor SU(3) can be extracted from the fully antisymmetric states in flavor SU(3). The stability of the dibaryon against the strong decay into two baryons is then discussed, by using the variational method within a constituent quark model with confining and color-spin interactions. To compare our results with those from lattice QCD in the flavor SU(3) limit, we search for the stable H-dibaryon in a wide range of π meson masses. We find that with the given potential, there is no compact six-quark dibaryon state in the SU(3) flavor symmetry broken case with realistic quark masses as well as in the flavor SU(3) symmetric case in a wide range of quark masses.
Akiyama, S; Akiyama, Satoru; Futami, Yasuhiko
2006-01-01
Mesonic fluctuations around the chiral solitons are investigated in the SU(3) chiral quark soliton model. Since the soliton takes the non-hedgehog shape for the hyperons and the hedgehog one for the non-hedgehog baryons in our approach, the fluctuations also change according to the baryonic state. The quantum corrections to the masses (the Casimir energies) are estimated for the octet and decuplet baryons. The lack of the confinement in this model demands the cutoff on the energy of the fluctuations. Under the assumption that the value of the cutoff energy is $2\\times$(the lightest constituent quark mass), these calculation reproduces the masses of the baryons within 15 % error.
Chiral restoration and deconfinement in two-color QCD with two flavors of staggered quarks
Energy Technology Data Exchange (ETDEWEB)
Scheffler, David; Scior, Philipp; Smith, Dominik [Institut fuer Kernphysik, Technische Universitaet Darmstadt (Germany); Schmidt, Christian [Fakultaet fuer Physik, Universitaet Bielefeld (Germany); Smekal, Lorenz von [Institut fuer Kernphysik, Technische Universitaet Darmstadt (Germany); Institut fuer Theoretische Physik, Justus-Liebig-Universitaet, Giessen (Germany)
2014-07-01
In preparation of lattice studies of the two-color QCD phase diagram we study chiral restoration and deconfinement at finite temperature with two flavors of staggered quarks using an RHMC algorithm on GPUs. We first study unquenching effects in local Polyakov loop distributions, and the Polyakov loop potential obtained via Legendre transformation, in a fixed-scale approach for heavier quarks. We also present the chiral condensate and the corresponding susceptibility over the lattice coupling across the chiral transition for lighter quarks. Using Ferrenberg-Swendsen reweighting we extract the maxima of the chiral susceptibility in order to determine pseudo-critical couplings on various lattices suitable for chiral extrapolations. These are then used to fix the relation between coupling and temperature in the chiral limit.
Double parton correlations in Light-Front constituent quark models
Directory of Open Access Journals (Sweden)
Rinaldi Matteo
2015-01-01
Full Text Available Double parton distribution functions (dPDF represent a tool to explore the 3D proton structure. They can be measured in high energy proton-proton and proton nucleus collisions and encode information on how partons inside a proton are correlated among each other. dPFDs are studied here in the valence quark region, by means of a constituent quark model, where two particle correlations are present without any additional prescription. This framework allows to understand the dynamical origin of the correlations and to clarify which, among the features of the results, are model independent. Use will be made of a relativistic light-front scheme, able to overcome some drawbacks of the previous calculation. Transverse momentum correlations, due to the exact treatment of the boosts, are predicted and analyzed. The role of spin correlations is also shown. Due to the covariance of the approach, some symmetries of the dPDFs are seen unambigously. For the valence sector, also the study of the QCD evolution of the model results, which can be performed safely thanks to the property of good support, has been also completed.
△△ Dibaryon Structure in Extended Chiral SU(3) Quark Model
Institute of Scientific and Technical Information of China (English)
DAI Lian-Rong
2005-01-01
@@ The structure of △△ dibaryon is studied in the extended chiral SU(3) quark model in which vector meson exchanges are included. The effect of the vector meson fields is very similar to that of the one-gluon exchange (OGE) interaction. Both in the chiral SU(3) quark model and in the extended chiral SU(3) quark model, the resultant mass of the △△ dibaryon is lower than the threshold of the △△ channel but higher than that of the△Nπ channel.
Current quarks, constituent quarks and the reactions K-p →πdegΛ *
International Nuclear Information System (INIS)
The transformation between current and constituent quarks is considered in view of the checking of the contributions, through PCAC, of the Σsup(*) resonances to the reactions K-p →πdegΛsup(*) (with negative parity) and the decays Σsup(*)→K-p and Σsup(*)→πdegΛsup(*). Both the Σsup(*) and Λsup(*) under consideration are classified in the 70.L=1 representation. In the considered model only one parameter is left, contrary to what happens in pure group-theoretical approach. The predictions are almost independent of its value and in good agreement with experiment
Nonequilibrium pion dynamics near the critical point in a constituent quark model
Boyanovsky, D; Wang, S Y
2003-01-01
We study static and dynamical critical phenomena of chiral symmetry breaking in a two-flavor Nambu--Jona-Lasinio constituent quark model. We obtain the low-energy effective action for scalar and pseudoscalar degrees of freedom to lowest order in quark loops and to quadratic order in the meson fluctuations around the mean field. The \\emph{static} limit of critical phenomena is shown to be described by a Ginzburg-Landau effective action including \\emph{spatial} gradients. Hence \\emph{static} critical phenomena is described by the universality class of the O(4) Heisenberg ferromagnet. \\emph{Dynamical} critical phenomena is studied by obtaining the equations of motion for pion fluctuations. We find that for $T
QCD topological susceptibility from the nonlocal chiral quark model
Nam, Seung-il
2016-01-01
We investigate the QCD topological susceptibility $\\chi_t$ by using the nonlocal chiral quark model (NL$\\chi$QM). This model is based on the liquid instanton QCD-vacuum configuration in which $\\mathrm{SU}(3)$ flavor symmetry is explicitly broken by the current quark mass $(m_{u,d},m_s)\\approx(5,135)$ MeV. To compute $\\chi_t$, the local topological charge density operator $Q_t(x)$ is derived from the effective partition function of NL$\\chi$QM. We take into account the contributions from the leading-order (LO) ones $\\sim\\mathcal{O}(N_c)$ in the $1/N_c$ expansion. We also verify that the analytical expression of $\\chi_t$ in NL$\\chi$QM satisfy the Witten-Veneziano (WV) and the Leutwyler-Smilga (LS) formulae. Once the average instanton size and inter-instanton distance are fixed with $\\bar{\\rho}=1/3$ fm and $\\bar{R}=1$ fm, respectively, all the associated model parameters are all determined self-consistently within the model, including the $\\eta$ and $\\eta'$ weak decay constants. We obtain the results such as $F_{...
Spontaneous chiral-symmetry breaking of lattice QCD with massless dynamical quarks
Institute of Scientific and Technical Information of China (English)
2007-01-01
One of the most challenging issues in QCD is the investigation of spontaneous chiral-symmetry breaking, which is characterized by the non-vanishing chiral condensate when the bare fermion mass is zero. In standard methods of the lattice gauge theory, one has to perform expensive simulations at multiple bare quark masses, and employ some modeled functions to extrapolate the data to the chiral limit. This paper applies the probability distribution function method to computing the chiral condensate in lattice QCD with massless dynamical quarks, without any ambiguous mass extrapolation. The results for staggered quarks indicate that this might be a promising and efficient method for investigating the spontaneous chiral-symmetry breaking in lattice QCD, which deserves further investigation.
Uniqueness of quarks, leptons and exotic fermions in the chiral-color models
International Nuclear Information System (INIS)
We study the uniqueness of quarks, leptons and exotic fermions in the chiral-color models of SU(3)CL x SU(2)L x U(1)Y and SU(3)CL x SU(3)CR x SU(2)L x SU(2)R x U(1) based on the cancellations of the three known chiral anomalies in four dimensions. The minimal exotic particles are identified for existing three and four quark-lepton families
Solitons in a chiral quark model with non-local interactions
Golli, B; Ripka, G; Golli, Bojan; Broniowski, Wojciech; Ripka, Georges
1998-01-01
Hedgehog solitons are found in a chiral quark model with non-local interactions. The solitons are stable without the chiral-circle constraint for the meson fields, as was assumed in previous Nambu-Jona--Lasinio model with local interactions.
Relativistic Quark Model Calculation of the l1, l2 Coefficients of the Chiral Lagrangian
Llanes-Estrada, Felipe J.; Bicudo, Pedro
2002-01-01
We briefly report on a relativistic quark model scheme to calculate the O(P^4) pion-pion vertex in the planar approximation and in the chiral limit. The calculation is reduced to the solution of simple integral equations (Bethe-Salpeter like) by an effective use of chiral Ward Identities. Specific model computations are provided.
Parton Distribution in Pseudoscalar Mesons with a Light-Front Constituent Quark Model
de Melo, J P B C; Tsushima, Kazuo
2015-01-01
We compute the distribution amplitudes of the pion and kaon in the light-front constituent quark model with the symmetric quark-bound state vertex function. In the calculation we explicitly include the flavor-SU(3) symmetry breaking effect in terms of the constituent quark masses of the up (down) and strange quarks. To calculate the kaon parton distribution functions~(PDFs), we use both the conditions in the light-cone wave function, i.e., when $\\bar{s}$ quark is on-shell, and when $u$ quark is on-shell, and make a comparison between them. The kaon PDFs calculated in the two different conditions clearly show asymmetric behaviour due to the flavor SU(3)-symmetry breaking implemented by the quark masses.
Symmetries and aggregates of quarks as constituents of hadrons
International Nuclear Information System (INIS)
The interest of the Lie algebra of the group SU(n) for the classification of hadrons and the description of some of their static properties is emphasized for n=3, 4, 6, 8. The cases n=3 and 4 allow to introduce the quark flavors (u,d,s,) and (u,d,c,s), respectively, and the consideration of the spin of hadrons leads to the chain SU(2m) contains SU(m) x SU(2). The hadrons are described as bound states or aggregates of quarks of type quark-quark-quark for baryons and quark-antiquark for mesons. The Pauli exclusion principle applied to the three-quark baryons requires the introduction of a new quantum number, the color: each flavor of quark then comes in three colors
Dynamical quarks effects on the gluon propagation and chiral symmetry restoration
Bashir, A; Rodríguez-Quintero, J
2014-01-01
We exploit the recent lattice results for the infrared gluon propagator with light dynamical quarks and solve the gap equation for the quark propagator. Chiral symmetry breaking and confinement (intimately tied with the analytic properties of QCD Schwinger functions) order parameters are then studied.
Spin Polarized versus Chiral Condensate in Quark Matter at Finite Temperature and Density
Matsuoka, H; da Providencia, J; Providencia, C; Yamamura, M; Bohr, H
2016-01-01
It is shown that the spin polarized condensate appears in quark matter at high baryon density and low temperature due to the tensor-type four-point interaction in the Nambu-Jona-Lasinio-type model as a low energy effective theory of quantum chromodynamics. It is indicated within this low energy effective model that the chiral symmetry is broken again by the spin polarized condensate as increasing the quark number density, while the chiral symmetry restoration occurs in which the chiral condensate disappears at a certain density.
sup 3 P sub 0 study of meson decays in a chiral quark model
Bonnaz, R; Silvestre-Brac, B; Fernández, F; Valcarce, A
2001-01-01
The strong decays of a meson into two mesons are studied in the framework of the sup 3 P sub 0 model. The meson wave functions are determined by means of a realistic chiral quark model constructed in the baryon sector and comparison is made with a traditional potential of 'Coulomb + linear' type. Two different forms for the creation vertex are analyzed. A momentum dependent vertex is proved to be definitively superior. The chiral quark model provides an overall good description of all known transitions and gives results of roughly the same quality as those obtained from phenomenological quark-antiquark potentials.
Soft matrix elements in the non-local chiral quark model
International Nuclear Information System (INIS)
In presence of the hard scale amplitudes for high energy processes factorize into perturbative and soft part. While the former can be calculated within QCD, the latter has to be either obtained from experiment or treated by non-perturbative methods. One of the possibilities is to use low energy effective models, which incorporate dynamical chiral symmetry breaking, as a one of the most important phenomena at this scale. Moreover, realistic models have to take into account the non-local interactions. In the present talk we consider semibosonized Nambu-Jona-Lasinio model, where the non-locality emerges as a momentum dependence of constituent quark mass. Technically, it serves as a natural way of Lorentz covariant regulator of the loop integrals at high momenta, which is needed in order to make the calculations finite. On the other hand, momentum dependence of the mass forces us to replace standard local currents by the non-local ones. Their precise form is in general not restricted, therefore they have to be modelled. In order to demonstrate simple choice of the non-local vector current, we use the photon distribution amplitudes and an ansatz for the momentum dependence of mass allowing for analytic calculations. As an example of the more advanced applications of the non-local chiral quark model (NCQM), we consider recently proposed pion-photon transition distribution amplitudes (TDA). They are in some sense similar to the ordinary generalized parton distribution functions, however they are non diagonal in the states - instead of transition between two hadrons with different momenta we deal with the hadron and the real photon. TDA's appear as a universal non perturbative input in backward Compton scattering or hadron-antihadron annihilation into two photons. From the point of view of the NCQM's TDA's are very interesting objects to study, because they have to satisfy several properties originating from Lorentz invariance (so called polynomiality), Ward identities and
Constituent quarks and the gluonic contribution to the spin of the nucleon
International Nuclear Information System (INIS)
The internal structure of the nucleon is more complicated than expected in a simple quark model. In particular, the portion of the nucleon spin carried by the spins of the quarks is not, as expected, of the order of one, but according to the experimental data much smaller. In this thesis we study the spin structure of the proton in quantum chromodynamics. The constituent quark model, based on SU(6), predicts that the spin of the proton should be carried by the quarks, in disagreement with the experiments. It appears strange, that the theoretical model works so well for the magnetic moments of the nucleons, but not for the spin, although the spin and the magnetic moments are closely related to each other. We shall resolve this problem by assuming that the constituent quarks have an internal structure on their own. Thus a constituent quark has a dynamical structure, and we can introduce notions like the quark or gluon distributions inside a constituent quark. In the light of new experimental data from HERMES, COMPASS, JLab, and RHIC-spin, the current status of our knowledge of the spin structure is discussed in the two theoretical frameworks: the naive parton model, and the QCD evolved parton model. QCD a is successful theory, both in perturbative and non-perturbative regions, but the spin of the nucleon still needs to be explained within QCD. (orig.)
How to Determine the Pion Cloud of the Constituent Quark
Baumgärtner, S; Pirner, H.J.; Königsmann, K.(Universität Freiburg, Physikalisches Institut, Freiburg, 79104, Germany); Povh, B.
1995-01-01
We calculate the differential cross section for semi-inclusive pion production in electron proton reactions using a model where the physical quark fluctuates with some probability to quark plus pion. The kinematic regions for a determination of this `pion cloud' are evaluated.
Electromagnetic properties of baryons in the constituent quark model
International Nuclear Information System (INIS)
The electromagnetic properties of baryons are investigated in the framework of a relativized quark model. The model includes beyond the usual single quark transition ansatz relativistic effects due to the strong interaction and confinement forces between the quarks. Furthermore the center-of-mass motion of the three-quark system is separated off in a Lorentz-invariant way. All relativistic correction terms are obtained by expanding the corresponding relativistic expressions in powers of the quark velocity. In this way recoil effects on the electromagnetic interaction between the photon and the baryon could be explicitly studied. Using the harmonic oscillator wavefunctions with the configuration mixing from the Isgur-Karl model, the form factors of the nucleon and the electromagnetic transition amplitudes both for longitudinally and transversely polarized photons are calculated for the most important baryon resonances. An extension to baryons involving strange quarks is also considered. Comparisons are made with the results of the nonrelativistic quark model and with some other approaches. (orig.)
Confinement and dynamical chiral symmetry breaking in a non-perturbative renormalizable quark model
Dudal, D.; Guimaraes, M. S.; Palhares, L. F.; Sorella, S. P.
2016-02-01
Inspired by the construction of the Gribov-Zwanziger action in the Landau gauge, we introduce a quark model exhibiting both confinement and chiral symmetry aspects. An important feature is the incorporation of spontaneous chiral symmetry breaking in a renormalizable fashion. The quark propagator in the condensed vacuum turns out to be of a confining type. Besides a real pole, it exhibits complex conjugate poles. The resulting spectral form is explicitly shown to violate positivity, indicative of its unphysical character. Moreover, the ensuing quark mass function fits well to existing lattice data. To further validate the physical nature of the model, we identify a massless pseudoscalar (i.e. a pion) in the chiral limit and present estimates for the ρ meson mass and decay constant.
The Hypercentral Constituent Quark Model and its symmetry
Giannini, M M
2015-01-01
The hypercentral CQM, which is inspired by Lattice QCD calculations for quark-antiquark potentials, is presented, stressing its underlying symmetry. Its results for the spectrum, the helicity amplitudes and the elastic form factors are briefly reported. In the latter case the model has allowed to show, for the first time in the framework of a quark model, that relativistic effects are responsible for a deviation from the usually accepted dipole behaviour, in agreement with recent data taken at the Jefferson Lab.
Instanton-dyon Ensemble with two Dynamical Quarks: the Chiral Symmetry Breaking
Larsen, Rasmus
2015-01-01
This is the second paper of the series aimed at understanding of the ensemble of the instanton-dyons, now with two flavors of light dynamical quarks. The partition function is appended by the fermionic factor, $(det T)^{N_f}$ and Dirac eigenvalue spectra at small values are derived from the numerical simulation of 64 dyons. Those spectra show clear chiral symmetry breaking pattern at high dyon density. Within current accuracy, the confinement and chiral transitions occur at very similar densities.
Chiral symmetry and quark-antiquark pair creation in a strong color-electromagnetic field
International Nuclear Information System (INIS)
We study the manifestation of chiral symmetry and q-q-bar pair creation in the presence of the external color-electromagnetic field, using the Nambu-Jona-Lasinio model. We derive the compact formulae of the effective potential, the Dyson equation for the dynamical quark mass and the q-q-bar pair creation rate in the covariantly constant color-electromagnetic field. Our results are compared with those in other approaches. The chiral-symmetry restoration takes place by a strong color-electric field, and the rapid reduction of the dynamical quark mass is found around the critical field strength, εcr≅4GeV/fm. Natural extension to the three-flavor case including s-quarks is also done. Around quarks or antiquarks, chiral symmetry would be restored by the sufficiently strong color-electric field, which may lead to the chiral bag picture of hadrons. For the early stage for ultrarelativistic heavy-ion collisions, the possibility of the chiral-symmetry restoration is indicated in the central region just after the collisions. (author)
Possible discovery channel for fourth chiral family up-quark at the LHC
Beser, S; Oner, B B; Sultansoy, S
2016-01-01
Resonant production of fourth chiral family up quark at the LHC via anomalous interactions have been analyzed. It is shown that search for resonances in W^{+}b final states could lead to discovery of the fourth chiral family and simultaneously determine scale of the new physics, presumabely related to the quark and lepton compositeness. Obtained results emphasize an importance of W-leading jet invariant mass analysis in search for W+jets final states at the LHC, both with and without b-tagging.
Confinement, quark mass functions, and spontaneous chiral symmetry breaking in Minkowski space
International Nuclear Information System (INIS)
We formulate the covariant equations for quark-antiquark bound states in Minkowski space in the framework of the Covariant Spectator Theory. The quark propagators are dressed with the same kernel that describes the interaction between different quarks. We show that these equations are charge conjugation invariant, and that in the chiral limit of vanishing bare quark mass, a massless pseudoscalar bound state is produced in a Nambu--Jona-Lasinio (NJL) mechanism, which is associated with the Goldstone boson of spontaneous chiral symmetry breaking. In this introductory paper we test the formalism by using a simplified kernel consisting of a momentum-space $\\delta$-function with a vector Lorentz structure, to which one adds a mixed scalar and vector confining interaction. The scalar part of the confining interaction is not chirally invariant by itself, but decouples from the equations in the chiral limit and therefore allows the NJL mechanism to work. With this model we calculate the quark mass function, and we compare our Minkowski-space results to LQCD data obtained in Euclidean space. In a companion paper we apply this formalism to a calculation of the pion form factor
International Nuclear Information System (INIS)
Overlap fermions are particularly well suited to study the finite temperature dynamics of the chiral symmetry restoration transition of QCD, which might be just an analytic crossover. Using gauge field configurations on a 243 x 10 lattice with Nf=2 flavours of dynamical Wilson-clover quarks generated by the DIK collaboration, we compute the lowest 50 eigenmodes of the overlap Dirac operator and try to locate the transition by fermionic means. We analyse the spectral density, local chirality and localisation properties of the low-lying modes and illustrate the changing topological and (anti-) selfdual structure of the underlying gauge fields across the transition. (orig.)
On the Chiral Quark Soliton Model with Pauli-Villars Regularization
Kubota, T.; Wakamatsu, M.; Watabe, T.
1999-01-01
The Pauli-Villars regularization scheme is often used for evaluating parton distributions within the framework of the chiral quark soliton model with inclusion of the vacuum polarization effects. Its simplest version with a single subtraction term should however be taken with some caution, since it does not fully get rid of divergences contained in scalar and psuedoscalar quark densities appearing in the soliton equation of motion. To remedy this shortcoming, we propose here its natural exten...
Institute of Scientific and Technical Information of China (English)
应和平; 董绍静; 张剑波
2003-01-01
With an exact chiral symmetry, overlap fermions allow us to reach very light quark region. In the minimummps = 179 MeV, the quenched chiral logarithm diverge is examined. The chiral logarithm parameter δ is calculatedfrom both the pseudo-scalar meson mass mp2s diverge channel and the pseudo-scalar decay constant f p channel.In both the cases, we obtain δ = 0.25 ± 0.03. We also observe that the quenchedchiral logarithm diverge occursonly in the mps ≤400 MeV region.
Ruggieri, M
2016-01-01
In this article we study spontaneous chiral symmetry breaking for quark matter in the background of an electric-magnetic flux tube with static, homogeneous and parallel electric field $\\bm E$ and magnetic field $\\bm B$. We use a Nambu-Jona-Lasinio model with a local kernel interaction to compute the relevant quantities to describe chiral symmetry breaking at finite temperature for a wide range of $E$ and $B$. We study the effect of the flux tube background on inverse catalysis of chiral symmetry breaking for $E$ and $B$ of the same order of magnitude. We then focus on the effect of equilibration of chiral density, $n_5$, produced dynamically by axial anomaly on the critical temperature. The equilibration of $n_5$, a consequence of chirality flipping processes in the thermal bath, allows for the introduction of the chiral chemical potential, $\\mu_5$, which is computed self-consistently as a function of temperature and field strength by coupling the number equation to the gap equation. We find that even if chir...
Pion Generalized Parton Distributions within a fully covariant constituent quark model
Fanelli, C; Romanelli, G; Salme', G; Salmistraro, M
2016-01-01
We extend the investigation of the Generalized Parton Distribution for a charged pion within a fully covariant constituent quark model, in two respects: (i) calculating the tensor distribution and (ii) adding the treatment of the evolution, needed for achieving a meaningful comparison with both the experimental parton distribution and the lattice evaluation of the so-called generalized form factors. Distinct features of our phenomenological covariant quark model are: (i) a 4D Ansatz for the pion Bethe-Salpeter amplitude, to be used in the Mandelstam formula for matrix elements of the relevant current operators, and (ii) only two parameters, namely a quark mass assumed to hold $m_q=~220$ MeV and a free parameter fixed through the value of the pion decay constant. The possibility of increasing the dynamical content of our covariant constituent quark model is briefly discussed in the context of the Nakanishi integral representation of the Bethe-Salpeter amplitude.
Pion generalized parton distributions within a fully covariant constituent quark model
Fanelli, Cristiano; Pace, Emanuele; Romanelli, Giovanni; Salmè, Giovanni; Salmistraro, Marco
2016-05-01
We extend the investigation of the generalized parton distribution for a charged pion within a fully covariant constituent quark model, in two respects: (1) calculating the tensor distribution and (2) adding the treatment of the evolution, needed for achieving a meaningful comparison with both the experimental parton distribution and the lattice evaluation of the so-called generalized form factors. Distinct features of our phenomenological covariant quark model are: (1) a 4D Ansatz for the pion Bethe-Salpeter amplitude, to be used in the Mandelstam formula for matrix elements of the relevant current operators, and (2) only two parameters, namely a quark mass assumed to be m_q=~220 MeV and a free parameter fixed through the value of the pion decay constant. The possibility of increasing the dynamical content of our covariant constituent quark model is briefly discussed in the context of the Nakanishi integral representation of the Bethe-Salpeter amplitude.
Supergrand exceptional unification and quark-lepton constituents
Energy Technology Data Exchange (ETDEWEB)
Baaklini, N.S. (International Centre for Theoretical Physics, Trieste (Italy))
1980-07-05
Supporting the possibility that matter and gauge fields may be supersymmetrically unified at very high energies, it is examined whether the presently known quark-lepton SU/sub 5/ or SO/sub 10/ multiplets can be accommodated among the considered gauge fermions.
Fragmentation functions of pions and kaons in the nonlocal chiral quark model
Directory of Open Access Journals (Sweden)
Kao Chung Wen
2014-03-01
Full Text Available We investigate the unpolarized pion and kaon fragmentation functions using the nonlocal chiral-quark model. In this model the interactions between the quarks and pseudoscalar mesons is manifested nonlocally. In addition, the explicit flavor SU(3 symmetry breaking effect is taken into account in terms of the current quark masses. The results of our model are evaluated to higher Q2 value Q2 = 4 GeV2 by the DGLAP evolution. Then we compare them with the empirical parametrizations. We find that our results are in relatively good agreement with the empirical parametrizations and the other theoretical estimations.
The effect of instanton-induced interaction on -wave meson spectra in constituent quark model
Indian Academy of Sciences (India)
Bhavyashri; S Sarangi; Godfrey Saldanha; K B Vijaya Kumar
2008-01-01
The mass spectrum of the -wave mesons is considered in a non-relativistic constituent quark model. The full Hamiltonian used in the investigation includes the kinetic energy, the confinement potential, the one-gluon-exchange potential (OGEP) and the instanton-induced quark-antiquark interaction (III). A good description of the mass spectrum is obtained. The respective role of III and OGEP in the P-wave meson spectrum is discussed.
Non-local regularization of chiral quark models in the soliton sector
Ripka, G; Ripka, Georges; Golli, Bojan
1999-01-01
A chiral quark model is described which is regularized in terms of Lorentz invariant non-local interactions. The model is regularized to all loop orders and it ensures the proper quantization of the baryon number. It sustains bound hedgehog solitons which, after suitable centre of mass corrections, can adequately describe the nucleon.
From Chiral quark dynamics with Polyakov loop to the hadron resonance gas model
Arriola, E. Ruiz; Megias, E.; Salcedo, L. L.
2012-01-01
Chiral quark models with Polyakov loop at finite temperature have been often used to describe the phase transition. We show how the transition to a hadron resonance gas is realized based on the quantum and local nature of the Polyakov loop.
Instantaneous Chiral Quark Model for Relativistic Mesons in a Hot and Dense Medium
International Nuclear Information System (INIS)
A chiral quark model with covariant instantaneous interactions is formulated using relativistic thermodynamic Green functions. The approach is applied to the description of mesons as relativistic bound state in hot and dense quark matter. The Schwinger-Dyson equation for the quark mass operator is obtained for a covariant four-point interaction kernel. The Salpeter equations for quark-antiquark bound states in a two-component relativistic quark plasma are given in the scalar-pseudoscalar as well as vector-axial-vector channels. The case of nonvanishing total momentum of bound state relative to the medium is considered. Numerical results for the meson mass spectrum and the pion decay constant at finite temperature are presented for the special case of a separable interaction which can be applied to the case of more realistic potentials. 36 refs., 7 figs
Dynamical quark loop light-by-light contribution to muon g-2 within the nonlocal chiral quark model
International Nuclear Information System (INIS)
The hadronic corrections to the muon anomalous magnetic moment aμ, due to the gauge-invariant set of diagrams with dynamical quark loop light-by-light scattering insertions, are calculated in the framework of the nonlocal chiral quark model. These results complete calculations of all hadronic light-by-light scattering contributions to aμ in the leading order in the 1/Nc expansion. The result for the quark loop contribution is aμHLbL,Loop = (11.0 ± 0.9) @ x 10-10, and the total result is aμHLbL,NχQM = (16.8 ± 1.2) @ x 10-10. (orig.)
Unifying Nucleon and Quark Dynamics at Finite Baryon Number Density
Meyer, J.; Schwenzer, K.; Pirner, H. -J.
1999-01-01
We present a model of baryonic matter which contains free constituent quarks in addition to bound constituent quarks in nucleons. In addition to the common linear sigma-model we include the exchange of vector-mesons. The percentage of free quarks increases with baryon density but the nucleons resist a restoration of chiral symmetry.
Alexandru, Andrei
2014-01-01
The validity of recently proposed equivalence between valence spontaneous chiral symmetry breaking (vSChSB) and chiral polarization of low energy Dirac spectrum (ChP) in SU(3) gauge theory, is examined for the case of twelve mass-degenerate fundamental quark flavors. We find that the vSChSB-ChP correspondence holds for regularized systems studied. Moreover, our results suggest that vSChSB occurs in two qualitatively different circumstances: there is a quark mass $m_c$ such that for $m > m_c$ the mode condensing Dirac spectrum exhibits standard monotonically increasing density, while for $m_{ch} < m < m_c$ the peak around zero separates from the bulk of the spectrum, with density showing a pronounced depletion at intermediate scales. Valence chiral symmetry restoration may occur at yet smaller masses $m < m_{ch}$, but this has not yet been seen by overlap valence probe, leaving the $m_{ch}=0$ possibility open. The latter option could place massless N$_f$=12 theory outside of conformal window. Anomalou...
Alexandru, Andrei; Horváth, Ivan
2016-01-01
The validity of recently proposed equivalence between valence spontaneous chiral symmetry breaking (vSChSB) and chiral polarization of low energy Dirac spectrum (ChP) in SU(3) gauge theory, is examined for the case of twelve mass-degenerate fundamental quark flavors. We find that the vSChSB-ChP correspondence holds for regularized systems studied. Moreover, our results suggest that vSChSB occurs in two qualitatively different circumstances: there is a quark mass mc such that for m > mc the mode condensing Dirac spectrum exhibits standard monotonically increasing density, while for mch < m < mc the peak around zero separates from the bulk of the spectrum, with density showing a pronounced depletion at intermediate scales. Valence chiral symmetry restoration may occur at yet smaller masses m < mch, but this has not yet been seen by overlap valence probe, leaving the mch = 0 possibility open. The latter option could place massless Nf=12 theory outside of conformal window. Anomalous behavior of overlap Dirac spectrum for mch < m < mc is qualitatively similar to one observed previously in zero and few-flavor theories as an effect of thermal agitation.
The transition potential of the quark-antiquark pair (meson) exchange in the constituent quark model
International Nuclear Information System (INIS)
The lowest-order of amplitude for the exchange of quark-antiquark pairs (q-q-bar) between two three-quark clusters (nucleons) are obtained by QCD perturbation theory when the two nucleons overlap, and thus the transition potential for the exchange of the color-singlet (q-q-bar) pairs (mesons) between the two nucleons is defined. The non-relativistic approximation of this transition potential is also discussed and the expression of the potential is consistent with the oneboson exchange one. The nucleon-meson vertex structure is consistently included in this potential due to the quark structure of the hadron
Constituent quark and hadronic structure in the next-to-leading order
International Nuclear Information System (INIS)
Structure of a constituent quark in calculated in the NLO. It is applied to generate the Structure function of Proton. It is found that SU(2) symmetry breaking is due to fluctuation of binding gluon to q-bar q pairs which contributes to the hadronic structure by as much as 3-5 percents. (author)
Reply to Comment on "Hara's theorem in the constituent quark model"
Dmitrašinović, V.
1998-01-01
In the preceding Comment it is alleged that a "hidden loophole" in the proof of Hara's theorem has been found, which purportedly invalidates the conclusions of the paper commented upon. I show that there is no such loophole in the constituent quark model, and that the "counterexample" presented in the Comment is not gauge invariant.
Nucleon Structure Functions from a Chiral Soliton
Weigel, H.(Physics Department, Stellenbosch University, Matieland 7602, South Africa); Gamberg, L.(Department of Physics, Penn State University-Berks, Reading, PA, 19610, U.S.A.); Reinhardt, H.
1996-01-01
Nucleon structure functions are studied within the chiral soliton approach to the bosonized Nambu-Jona-Lasinio model. The valence quark approximation is employed which is justified for moderate constituent quark masses ($\\sim$ 400 MeV) as the contribution of the valence quark level dominates the predictions of nucleon properties. As examples the unpolarized structure functions for the ${\
A chiral matrix model of the semi-Quark Gluon Plasma in QCD
Pisarski, Robert D
2016-01-01
A chiral matrix model applicable to QCD with 2+1 flavors is developed. This requires adding a SU(3)_L x SU(3)_R x Z(3)_A nonet of scalar fields, with both parities, and coupling these to quarks through a Yukawa coupling, y. Treating the scalar fields in mean field approximation, the effective Lagrangian is computed by integrating out quarks to one loop order. In addition to the usual symmetry breaking term, linear in the current quark mass m_qk, at a nonzero temperature T it is necessary to add a new term, ~ m_qk T^2. The parameters of the gluon part of the matrix model, including especially the deconfining transition temperature T_d = 270 MeV, are identical to that for the pure glue theory without quarks. The parameters in the chiral matrix model are fixed by the values, at zero temperature, of the pion decay constant the masses of the pions, kaons, eta, and eta'. The temperature for the chiral crossover at T_chi = 155 MeV is determined by adjusting the Yukawa coupling y. We find reasonable agreement with th...
EMC-SLAC effect from quark clustering and constituent quark Fermi motion and mass
International Nuclear Information System (INIS)
The A-dependence of the EMC-effect, as recently measured at SLAC, has been calculated from the probability of forming > 3q clusters, by using the space-time wavefunction of valence quarks, and assuming nuclei to be in hexagonal or cubic dense packing. A fair fit to the x-distributions of sigmasub(A)/sigmasub(d) is obtained, investing the valence quark's average Fermi momentum and mass from our previous determinations. (orig.)
The baryon spectrum and the hypercentral Constituent Quark Model
Giannini, M M
2015-01-01
The description of the baryon spectrum is performed using the hypercentral Consituent Quark Model (hCQM), mainly in comparison with the harmonic oscillator (h.o.). Recentlly many new states, at various levels of confidence have been observed, leading to a softening of the missing resonance problem in the case of positive parity states. However, the number of negative states is higher that predicted by the commonly used h.o. scheme and therefore one is forced to take into account also the higher energy shells, which contain an overall number of states much greater than the observed one. It is shown that, thanks to the peculiar level scheme of the hCQM, the recently observed negative parity states can be considered as belonging to the lower shells, keeping the missing resonance problem within more acceptable limits.
Inhomogeneous chiral phases in two-flavor quark matter
Abuki, Hiroaki
2015-01-01
We present a systematic study of the phase structure of QCD in a generalized Ginzburg-Landau framework. We find, going up in density, a strongly interacting matter might go through the "pion crystal", an exotic inhomogeneous chiral phase before reaching the full restoration of symmetry.
OZI violating eight-quark interactions as a thermometer for chiral transitions
Osipov, A A; Moreira, J; Blin, A H
2008-01-01
This work is a follow-up of our recent observation that in the SU(3) flavor limit with vanishing current quark masses the temperature for the chiral transition is substantially reduced by adding eight-quark interactions to the Nambu - Jona-Lasinio Lagrangian with U_A(1) breaking. Here we generalize the case to realistic light and strange quark masses and confirm our prior result. Additionally, we demonstrate that depending on the strength of OZI violating eight-quark interactions, the system undergoes either a rapid crossover or a first order phase transition. The meson mass spectra of the low lying pseudoscalars and scalars at T=0 are not sensitive to the difference in the parameter settings that correspond to these two alternatives, except for the singlet-octet mixing scalar channels, mainly the sigma meson.
Instability of the hedgehog shape for the octet baryon in the chiral quark soliton model
Akiyama, S; Akiyama, Satoru; Futami, Yasuhiko
2003-01-01
In this paper the stability of the hedgehog shape of the chiral soliton is studied for the octet baryon with the SU(3) chiral quark soliton model. The strangeness degrees of freedom are treated by a simplified bound-state approach, which omits the locality of the kaon wave function. The mean field approximation for the flavor rotation is applied to the model. The classical soliton changes shape according to the strangeness. The baryon appears as a rotational band of the combined system of the deformed soliton and the kaon.
Magnetic catalysis and inverse magnetic catalysis in nonlocal chiral quark models
Pagura, V P; Noguera, S; Scoccola, N N
2016-01-01
We study the behavior of strongly interacting matter under an external constant magnetic field in the context of nonlocal chiral quark models within the mean field approximation. We find that at zero temperature the behavior of the quark condensates shows the expected magnetic catalysis effect, our predictions being in good quantitative agreement with lattice QCD results. On the other hand, in contrast to what happens in the standard local Nambu-Jona-Lasinio model, when the analysis is extended to the case of finite temperature our results show that nonlocal models naturally lead to the Inverse Magnetic Catalysis effect.
Dynamical evolution of the chiral magnetic effect: applications to the quark-gluon plasma
Manuel, Cristina
2015-01-01
We study the dynamical evolution of the so-called chiral magnetic effect in an electromagnetic conductor. To this end, we consider the coupled set of corresponding Maxwell and chiral anomaly equations, and we prove that these can be derived from chiral kinetic theory. After integrating the chiral anomaly equation over space in a closed volume, it leads to a quantum conservation law of the total helicity of the system. A change in the magnetic helicity density comes together with a modification of the chiral fermion density. We study in Fourier space the coupled set of anomalous equations and we obtain the dynamical evolution of the magnetic fields, magnetic helicity density, and chiral fermion imbalance. Depending on the initial conditions we observe how the helicity might be transferred from the fermions to the magnetic fields, or vice versa, and find that the rate of this transfer also depends on the scale of wavelengths of the gauge fields in consideration. We then focus our attention on the quark-gluon pl...
Quark model with chiral-symmetry breaking and confinement in the Covariant Spectator Theory
Directory of Open Access Journals (Sweden)
Biernat Elmar P.
2016-01-01
Full Text Available We propose a model for the quark-antiquark interaction in Minkowski space using the Covariant Spectator Theory. We show that with an equal-weighted scalar-pseudoscalar structure for the confining part of our interaction kernel the axial-vector Ward-Takahashi identity is preserved and our model complies with the Adler-zero constraint for π-π-scattering imposed by chiral symmetry.
Quark model with chiral-symmetry breaking and confinement in the Covariant Spectator Theory
Biernat, Elmar P; Ribeiro, J E; Stadler, A; Gross, F
2015-01-01
We propose a model for the quark-antiquark interaction in Minkowski space using the Covariant Spectator Theory. We show that with an equal-weighted scalar-pseudoscalar structure for the confining part of our interaction kernel the axial-vector Ward-Takahashi identity is preserved and our model complies with the Adler-zero constraint for pi-pi-scattering imposed by chiral symmetry.
Quark model with chiral-symmetry breaking and confinement in the Covariant Spectator Theory
Biernat, Elmar P.; Peña, M. T.; Ribeiro, J. E.; Stadler, A.; Gross, F.
2016-03-01
We propose a model for the quark-antiquark interaction in Minkowski space using the Covariant Spectator Theory. We show that with an equal-weighted scalar-pseudoscalar structure for the confining part of our interaction kernel the axial-vector Ward-Takahashi identity is preserved and our model complies with the Adler-zero constraint for π-π-scattering imposed by chiral symmetry.
Quark model with chiral-symmetry breaking and confinement in the Covariant Spectator Theory
Energy Technology Data Exchange (ETDEWEB)
Biernat, Elmer P. [CFTP, Instituto Superior TÃ©cnico, Universidade de Lisboa, 1049-001 Lisboa, Portugal; Pena, Maria Teresa [CFTP, Instituto Superior TÃ©cnico, Universidade de Lisboa, 1049-001 Lisboa, Portugal; Departamento de FÃsica, Instituto Superior TÃ©cnico, Universidade de Lisboa, 1049-001 Lisboa, Portugal; Ribiero, Jose' Emilio F. [CeFEMA, Instituto Superior TÃ©cnico, Universidade de Lisboa, 1049-001 Lisboa, Portugal; Stadler, Alfred [Departamento de FÃsica, Universidade de Ãvora, 7000-671 Ãvora, Portugal; Gross, Franz L. [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
2016-03-01
We propose a model for the quark-antiquark interaction in Minkowski space using the Covariant Spectator Theory. We show that with an equal-weighted scalar-pseudoscalar structure for the confining part of our interaction kernel the axial-vector Ward-Takahashi identity is preserved and our model complies with the Adler-zero constraint for pi-pi-scattering imposed by chiral symmetry.
Eta and kaon production in a chiral quark model
Golli, Bojan
2016-01-01
We apply a coupled-channel formalism incorporating quasi-bound quark-model states to calculate pion scattering into eta N, K Lambda and K Sigma channels, as well eta p, eta n, K+Lambda, and K0Sigma+ photo-production processes. The meson-baryon and photon-baryon vertices are determined in a SU(3) version of the Cloudy Bag Model. Our model predicts sizable amplitudes in the P11, P13, P33 and S11 partial waves in agreement with the latest MAID isobar model and the recent partial-wave analyses of the Bonn-Gatchina group. We are able to give a quark-model explanation for the apparent resonance at 1685 MeV in the eta n channel.
Momentum scale dependence of the net quark number fluctuations near chiral crossover
International Nuclear Information System (INIS)
We investigate properties of the net baryon number fluctuations near chiral crossover in a hot and dense medium of strongly interacting quarks. The chirally invariant quark–antiquark interactions are modeled by an effective quark–meson Lagrangian. To preserve remnants of criticality in the O(4) universality class, we apply the functional renormalization group method to describe thermodynamics near chiral crossover. Our studies are focused on the influence of the momentum cuts on the critical behavior of different cumulants of the net quark number fluctuations. We use the momentum scale dependence of the flow equation to examine how the suppression of the momentum modes in the infrared and ultraviolet regimes modifies generic properties of fluctuations expected in the O(4) universality class. We show that the pion mass mπ is a natural soft momentum scale at which cumulants are saturated at their critical values, whereas for scales larger than 2mπ the characteristic O(4) structure of the higher-order cumulants gets lost. These results indicate that when measuring fluctuations of the net baryon number in heavy ion collisions to search for a partial restoration of chiral symmetry or critical point, special care must be taken when introducing kinematical cuts on the fluctuation measurements
International Nuclear Information System (INIS)
We study the color confinement, the qq pair creation and the dynamical chiral-symmetry breaking of nonperturbative QCD by using the dual Ginzburg-Landau theory, where the dual Higgs mechanism plays an essential role in the nonperturbative dynamics in the infrared region. As a result of the dual Meissner effect, the linear static quark potential, which characterizes the quark confinement, is obtained in the long distance within the quenched approximation. We obtain a simple expression for the string tension similar to the energy per unit length of a vortex in the superconductivity physics. The dynamical effect of light quarks on the quark confining potential is investigated in terms of the infrared screening effect due to the qq pair creation or the cut of the hadronic string. The screening length of the potential is estimated by using the Schwinger formula for the qq pair creation. We introduce the corresponding infrared cutoff to the strong long-range correlation factor in the gluon propagator as a dynamical effect of light quarks, and obtain a compact formula for the quark potential including the screening effect in the infrared region. We investigate the dynamical chiral-symmetry breaking by using the Schwinger-Dyson equation in the dual Ginzburg-Landau theory, where the gluon propagator includes the nonperturbative effect related to the color confinement. We find a large enhancement of the chiral-symmetry breaking by the dual Higgs mechanism, which supports the close relation between the color confinement and the chiral-symmetry breaking. The dynamical quark mass, the pion decay constant and the quark condensate are well reproduced by using the consistent values of the gauge coupling constant and the QCD scale parameter with the perturbative QCD and the quark confining potential. The light-quark confinement is also roughly examined in terms of the disappearance of physical poles in the light-quark propagator by using the smooth extrapolation of the quark mass
Exact heavy to light meson form factors in the combined heavy quark, large Nc and chiral limits
International Nuclear Information System (INIS)
We demonstrate that the form factors of local operators between a heavy meson state (like the B) and a light pseudoscalar state (like the pion) are given exactly by a single pole form in the combined heavy quark, large Nc (number of colors) and chiral limits. We discuss the deviations from this exact result from finite heavy quark masses, non-zero light quark masses and finite Nc. We comment on some of the numerous implications of this result
Top quark mass bounds in the hierarchical chiral symmetry-breaking framework
International Nuclear Information System (INIS)
By taking account of recent information on the Bd - antiBd mixing parameter, xd, and the product BB f2B, as well as uncertainties in the lighter quark masses, we are able to set search limits on the top quark mass of 84 ± 8 GeV for the Fritzsch mass matrices with two Higgs doublets or 78 ± 12 GeV for a modified set of Fritzsch mass matrices with minimal Higgs structure. We comment on the discovery complications involved when the top mass is very close to the W mass. If no top quark is eventually found with mass less than 100 - 110 GeV, the whole 3-family hierarchical chiral symmetry-breaking framework proposed by Fritzsch is ruled out
Strong decays of N~*(1535) in an extended chiral quark model
Institute of Scientific and Technical Information of China (English)
无
2009-01-01
The strong decays of the N*(1535) resonance are investigated in an extended chiral quark model by including the low-lying qqqqq components in addition to the qqq component.The results show that these five-quark components in N*(1535) contribute significantly to the N*(1535)→ Nπ and N*(1535) → Nη decays.The contributions to the Nη decay come from both the lowest energy and the next-to-lowest energy five-quarks components,while the contributions to the Nπ decay come from only the latter one.Taking these contributions into account,the description for the strong decays of N*(1535) is improved,especially for the puzzling large ratio of the decays to Nη and Nπ.
Constituent Quarks and Gluons, Polyakov loop and the Hadron Resonance Gas Model *,**
Directory of Open Access Journals (Sweden)
Megías E.
2014-03-01
Full Text Available Based on first principle QCD arguments, it has been argued in [1] that the vacuum expectation value of the Polyakov loop can be represented in the hadron resonance gas model. We study this within the Polyakov-constituent quark model by implementing the quantum and local nature of the Polyakov loop [2, 3]. The existence of exotic states in the spectrum is discussed.
Constituent Quarks and Gluons, Polyakov loop and the Hadron Resonance Gas Model *,**
Megías E.; Arriola E. Ruiz; Salcedo L.L.
2014-01-01
Based on first principle QCD arguments, it has been argued in arXiv:1204.2424[hep-ph] that the vacuum expectation value of the Polyakov loop can be represented in the hadron resonance gas model. We study this within the Polyakov-constituent quark model by implementing the quantum and local nature of the Polyakov loop hep-ph/0412308, hep-ph/0607338. The existence of exotic states in the spectrum is discussed.
Constituent quarks and proton break-up in p-A collisions at the AGS
Cole, B A
1999-01-01
Results are presented from BNL experiment 910 on the centrality and target dependence of projectile stopping, LAMBDA and K sup 0 sub S production, and pi sup - production in p-A collisions. The data, taken together, suggest that the 'stopping' of the baryon number and the stopping of the energy carried by the incident baryon in p-A collisions proceeds via different physical processes. We discuss a possible interpretation of the data in terms of constituent or valence quark interactions.
Structures of (ΩΩ)0+ and (([1])Ω)1+ in Extended Chiral SU(3) Quark Model
Institute of Scientific and Technical Information of China (English)
ZHANG Zong-Ye; YU You-Wen; DAI Lian-Rong
2003-01-01
The structures of (ΩΩ)0+ and (([1])Ω)1+ are studied in the extended chiral SU(3) quark model in whichvector meson exchanges are included. The effect from the vector meson fields is very similar to that from the one-gluonexchange (OGE) interaction. Both in the chiral SU(3) quark model and in the extended chiral SU(3) quark model,di-omega (ΩΩ)0+ is always deeply bound, with over one hundred MeV binding energy, and (([1])Ω)1+ 's binding energyis around 20 MeV. An analysis shows that the quark exchange effect plays a very important role for making di-omega(ΩΩ)0+ deeply bound.
International Nuclear Information System (INIS)
The chiral magnetic wave is a gapless collective excitation of quark-gluon plasma in the presence of an external magnetic field that stems from the interplay of chiral magnetic and chiral separation effects; it is composed of the waves of the electric and chiral charge densities coupled by the axial anomaly. We consider a chiral magnetic wave at finite baryon density and find that it induces the electric quadrupole moment of the quark-gluon plasma produced in heavy ion collisions: the 'poles' of the produced fireball (pointing outside of the reaction plane) acquire additional positive electric charge, and the 'equator' acquires additional negative charge. We point out that this electric quadrupole deformation lifts the degeneracy between the elliptic flows of positive and negative pions leading to v2(π+)2(π-), and estimate the magnitude of the effect.
Boughezal, Radja; Melnikov, Kirill
2011-01-01
The hadronic light-by-light scattering contribution to the muon anomalous magnetic moment can be estimated by computing constituent quark loops. Such an estimate is very sensitive to the numerical values of the constituent quark masses. These can be fixed by computing the hadronic vacuum polarization contribution to the muon magnetic anomaly within the same model. In this Letter, we demonstrate the stability of this framework against first-order perturbative QCD corrections.
Brazovskii-Dyugaev effect on the inhomogeneous chiral transition in quark matter
Karasawa, Shintaro; Lee, Tong-Gyu; Tatsumi, Toshitaka
2016-04-01
We investigate the effects of quantum and thermal fluctuations on the phase boundary between the inhomogeneous chiral phase and the chiral-restored phase in the phase diagram in the plane of temperature and chemical potential. Introducing the composite fields made of quark bilinear fields, we construct an effective action for them in quark matter by way of the correlation function method. Utilizing this effective action, we discuss the effects of the quark-antiquark and particle-hole pair fluctuations to find possible modifications of the vertex functions of the order parameter included in the thermodynamic potential. We find that the most important effect of the pair fluctuations is to change the sign of the fourth-order vertex function to make the phase transition always the first, rather than the second, order (we call it the Brazovskii-Dyugaev effect). Another important effect manifests in the second-order vertex function: it exhibits a singular behavior near the critical point, which prohibits the second-order phase transition. It, together with the fourth-order vertex function, alters the location of the phase boundary.
The B=2 system in the chiral quark-soliton model with broken scale invariance
Sarti, Valentina Mantovani; Vento, Vicente
2013-01-01
We study the interaction between two B=1 states in the Chiral-Dilaton Model with scale invariance where baryons are described as non-topological solitons arising from the interaction of chiral mesons and quarks. By using the hedgehog solution for the B=1 states we construct, via a product ansatz, three possible B=2 configurations to analyse the role of the relative orientation of the hedgehog quills in the dynamics. We investigate the behaviour of these solutions in the range of long and intermediate distances between the two solitons. Since the product ansatz breaks down as the two solitons get close, we explore the short range distances regime by building up a six quarks bag and by evaluating the interaction energy as a function of the inter-soliton separation. We calculate the interaction energy as a function of the inter-soliton distance for the B=2 system and we show that for small separations the six quarks bag, assuming a hedgehog structure, provides a stable bound state that at large separations conne...
Chiral Quark-Meson model of N and DELTA with vector mesons
International Nuclear Information System (INIS)
Vector mesons rho, A1 and ω are introduced in the Chiral Quark-Meson Theory (CQMT) of N and Δ. We propose a new viewpoint for developing CQMT from QCD at the mean-field level. The SU(2) x SU(2) chiral Lagrangian incorporates universal coupling. Accordingly, rho is coupled to the conserved isospin current, A to the partially conserved axial-vector current (PCAC), and ω to the conserved baryon current. As a result the only parameter of the model not directly related to experiment is the quark-pion coupling constant. A fully self-consistent mean-field solution to the model is found for fields in the hedgehog ansatz. The vector mesons play a very important role in the system. They contribute significantly to the values of observables and produce a high-quality fit to many data. The classical stability of the system with respect to hedgehog excitations is analyzed through the use of the Quark-Meson RPA equations (QMRPA)
Electromagnetic excitation of baryonic resonances up to 2 GeV in the constituent quark model
International Nuclear Information System (INIS)
The present thesis describes the electromagnetic excitation of baryonic resonances up to 2 GeV in the constituent quark model. A given baryon spectrum is tested in exclusive two-particle reactions and cross sections as well as polarization observables are calculated. For this a formalism for the calculation of general polarization observables in exclusive two-particle reaction is presented and applied to the photoproduction of pseudoscalar mesons and the Compton scattering. Resonant and non-resonant contributions to the scattering amplitude are derived in the framework of a Feshbach projection formalism and by this calculated consistently with the baryon spectrum. For photoinduced reactions a multipole analysis is performed and characteristic angular distributions of the cross section and simple polarization observables are studied. The photon-baryon vertex function is derived from the simple photon-quark vertex and decomposed in transverse and longitudinal quark momenta. The magnetic quark moment is modified by addition of vector-dominance contributions, and the spin-orbit correction terms are calculated. The results for two differnt baryon spectra are shown and discussed. (HSI)
International Nuclear Information System (INIS)
Three version of a model with colour excitations of constituent quarks are examined using inclusive leading proton and antiproton spectra in nuclear interactions at high energies. The comparison with experimental data excludes the models in which fragmentation into leading final hadrons depends only on the colour charge of constituents in an intermediate system. (author)
Kaon semileptonic decay (K_{l3}) form factor in the nonlocal chiral quark model
Nam, Seung-il
2007-01-01
We investigate the kaon semileptonic decay (K_{l3}) form factors within the framework of the nonlocal chiral quark model from the instanton vacuum, taking into account the effects of flavor SU(3) symmetry breaking. All theoretical calculations are carried out without any adjustable parameter. We also show that the present results satisfy the Callan-Treiman low-energy theorem as well as the Ademollo-Gatto theorem. It turns out that the effects of flavor SU(3) symmetry breaking are essential in reproducing the kaon semileptonic form factors. The present results are in a good agreement with experiments, and are compatible with other model calculations.
Classifying the Phases of Gauge Theories by Spectral Density of Probing Chiral Quarks
Alexandru, Andrei
2015-01-01
We describe our recent proposal that distinct phases of gauge theories with fundamental quarks translate into specific types of low-energy behavior in Dirac spectral density. The resulting scenario is built around new evidence substantiating the existence of a phase characterized by bimodal (anomalous) density, and corresponding to deconfined dynamics with broken valence chiral symmetry. We argue that such anomalous phase occurs quite generically in these theories, including in "real world" QCD above the crossover temperature, and in zero-temperature systems with many light flavors.
Generalized Ginzburg–Landau approach to inhomogeneous phases in nonlocal chiral quark models
International Nuclear Information System (INIS)
We analyze the presence of inhomogeneous phases in the QCD phase diagram within the framework of nonlocal chiral quark models. We concentrate in particular in the positions of the tricritical (TCP) and Lifshitz (LP) points, which are studied in a general context using a generalized Ginzburg–Landau approach. We find that for all the phenomenologically acceptable model parametrizations considered the TCP is located at a higher temperature and a lower chemical potential in comparison with the LP. Consequently, these models seem to favor a scenario in which the onset of the first order transition between homogeneous phases is not covered by an inhomogeneous, energetically favored phase
$Z_b(10650)$ and $Z_b(10610)$ states in a chiral quark model
Li, M. T.; Wang, W L; Dong, Y. B.; Zhang, Z. Y.
2012-01-01
We perform a systematic study of $B\\bar{B}^*$, $B^*\\bar{B}^*$, $D\\bar{D}^*$ and $D^*\\bar{D}^*$ systems by using effective interaction in our chiral quark model. Our results show that the interactions of $B\\bar{B}^*$, $B^*\\bar{B}^*$, $D\\bar{D}^*$ and $D^*\\bar{D}^*$ states are attractive, which consequently result in $B\\bar{B}^*$, $B^*\\bar{B}^*$, $D\\bar{D}^*$ and $D^*\\bar{D}^*$ bound states. The recent observed exotic-like hadrons of $Z_b(10610)$ and $Z_b(10650)$ are, therefore in our approach,...
Pion-to-photon transition distribution amplitudes in the non-local chiral quark model
Kotko, Piotr
2008-01-01
We apply the non-local chiral quark model to study vector and axial pion-to-photon transition amplitudes that are needed as a nonperturbative input to estimate the cross section of pion annihilation into the real and virtual photon. We use a simple form of the non-locality that allows to perform all calculations in the Minkowski space and guaranties polynomiality of the TDA's. We note only residual dependence on the precise form of the cut-off function, however vector TDA that is symmetric in skewedness parameter in the local quark model is no longer symmetric in the non-local case. We calculate also the transition form-factors and compare them with existing experimental parametrizations.
Pion-to-Photon Transition Distribution Amplitudes in the Non-Local Chiral Quark Model
Kotko, P.; Praszałowicz, M.
2009-01-01
We apply the non-local chiral quark model to study vector and axial pion-to-photon transition amplitudes that are needed as a nonperturbative input to estimate the cross-section of pion annihilation into the real and virtual photon. We use a simple form of the non-locality that allows to perform all calculations in the Minkowski space and guaranties polynomiality of the TDAs. We note only residual dependence on the precise form of the cut-off function, however vector TDA that is symmetric in skewedness parameter in the local quark model is no longer symmetric in the non-local case. We calculate also the transition form-factors and compare them with existing experimental parametrizations.
Constituent-quark model of nucleon and O + U → μμ-bar + X processes
International Nuclear Information System (INIS)
Using constituent-quark model of nucleon, the authors have calculated nucleon structure-functions of oxygen nucleus and uranium nucleus, and with which O + U → μμ-bar + X Drell-Yan processes have been analysed. The evaluated cross sections are in good agreement with recent data of the NA38 Group. It has been shown the total influence of all nuclear effects acting on these cross sections could change its magnitude even about 15%, thus the nuclear effects should not be neglected when discussing problems such as searching quark gluon plasma in the suppression phenomenon of J/ψ yields. Further more, phenomenological analysis shows that the K factor which characterizes contribution of perturbative QCD in this process decreases slowly as the lepton pair mass m increases, which is consistent with asymptotic freedom of QCD and agrees with previous results on this problem
Dynamics and Stability of Chiral Fluid
Mishustin, Igor N.; Koide, Tomoi; Denicol, Gabriel S.; Torrieri, Giorgio
2014-01-01
Starting from the linear sigma model with constituent quarks we derive the chiral fluid dynamics where hydrodynamic equations for the quark fluid are coupled to the equation of motion for the order-parameter field. In a static system at thermal equilibrium this model leads to a chiral phase transition which, depending on the choice of the quark-meson coupling constant, could be a crossover or a first order one. We investigate the stability of the chiral fluid in the static and expanding backg...
Lattice QCD analysis for relation between quark confinement and chiral symmetry breaking
Energy Technology Data Exchange (ETDEWEB)
Doi, Takahiro M.; Suganuma, Hideo [Department of Physics, Graduate School of Science, Kyoto University, Kitashirakawa-oiwake, Sakyo, Kyoto 606-8502 (Japan); Iritani, Takumi [Yukawa Institute for Theoretical Physics, Kyoto University, Kitashirakawa-Oiwake, Sakyo, Kyoto 606-8502 (Japan)
2016-01-22
The Polyakov loop and the Dirac modes are connected via a simple analytical relation on the temporally odd-number lattice, where the temporal lattice size is odd with the normal (nontwisted) periodic boundary condition. Using this relation, we investigate the relation between quark confinement and chiral symmetry breaking in QCD. In this paper, we discuss the properties of this analytical relation and numerically investigate each Dirac-mode contribution to the Polyakov loop in both confinement and deconfinement phases at the quenched level. This relation indicates that low-lying Dirac modes have little contribution to the Polyakov loop, and we numerically confirmed this fact. From our analysis, it is suggested that there is no direct one-to-one corresponding between quark confinement and chiral symmetry breaking in QCD. Also, in the confinement phase, we numerically find that there is a new “positive/negative symmetry” in the Dirac-mode matrix elements of link-variable operator which appear in the relation and the Polyakov loop becomes zero because of this symmetry. In the deconfinement phase, this symmetry is broken and the Polyakov loop is non-zero.
Lattice QCD analysis for relation between quark confinement and chiral symmetry breaking
Doi, Takahiro M.; Suganuma, Hideo; Iritani, Takumi
2016-01-01
The Polyakov loop and the Dirac modes are connected via a simple analytical relation on the temporally odd-number lattice, where the temporal lattice size is odd with the normal (nontwisted) periodic boundary condition. Using this relation, we investigate the relation between quark confinement and chiral symmetry breaking in QCD. In this paper, we discuss the properties of this analytical relation and numerically investigate each Dirac-mode contribution to the Polyakov loop in both confinement and deconfinement phases at the quenched level. This relation indicates that low-lying Dirac modes have little contribution to the Polyakov loop, and we numerically confirmed this fact. From our analysis, it is suggested that there is no direct one-to-one corresponding between quark confinement and chiral symmetry breaking in QCD. Also, in the confinement phase, we numerically find that there is a new "positive/negative symmetry" in the Dirac-mode matrix elements of link-variable operator which appear in the relation and the Polyakov loop becomes zero because of this symmetry. In the deconfinement phase, this symmetry is broken and the Polyakov loop is non-zero.
Lattice QCD analysis for relation between quark confinement and chiral symmetry breaking
International Nuclear Information System (INIS)
The Polyakov loop and the Dirac modes are connected via a simple analytical relation on the temporally odd-number lattice, where the temporal lattice size is odd with the normal (nontwisted) periodic boundary condition. Using this relation, we investigate the relation between quark confinement and chiral symmetry breaking in QCD. In this paper, we discuss the properties of this analytical relation and numerically investigate each Dirac-mode contribution to the Polyakov loop in both confinement and deconfinement phases at the quenched level. This relation indicates that low-lying Dirac modes have little contribution to the Polyakov loop, and we numerically confirmed this fact. From our analysis, it is suggested that there is no direct one-to-one corresponding between quark confinement and chiral symmetry breaking in QCD. Also, in the confinement phase, we numerically find that there is a new “positive/negative symmetry” in the Dirac-mode matrix elements of link-variable operator which appear in the relation and the Polyakov loop becomes zero because of this symmetry. In the deconfinement phase, this symmetry is broken and the Polyakov loop is non-zero
Next-to-leading-order constituent quark structure and hadronic structure functions
International Nuclear Information System (INIS)
We utilize the existing next-to-leading-order (NLO) formalism to calculate the partonic structure of a constituent quark. The structure of any hadron can be obtained thereafter using a convolution method. Such a procedure is used to generate the structure functions of protons and pions in NLO, neglecting certain corrections to ΛQCD. It is shown that while the constituent quark structure is generated purely perturbatively and accounts for the most part of the hadronic structure, there is a few percent contribution coming from the nonperturbative sector in the hadronic structure. This contribution plays the key role in explaining the SU(2) symmetry breaking of the nucleon sea and the observed violation of the Gottfried sum rule. These effects are calculated. We obtained an excellent agreement with the experimental data in a wide range of x=[10-6,1] and Q2=[0.5,5000] GeV2 for the proton structure function. We have also calculated pion structure and compared it with the existing data. Again, the model calculations agree rather well with the data from experiment
Next-to-leading-order constituent quark structure and hadronic structure functions
Arash, Firooz; Khorramian, Ali N.
2003-04-01
We utilize the existing next-to-leading-order (NLO) formalism to calculate the partonic structure of a constituent quark. The structure of any hadron can be obtained thereafter using a convolution method. Such a procedure is used to generate the structure functions of protons and pions in NLO, neglecting certain corrections to ΛQCD. It is shown that while the constituent quark structure is generated purely perturbatively and accounts for the most part of the hadronic structure, there is a few percent contribution coming from the nonperturbative sector in the hadronic structure. This contribution plays the key role in explaining the SU(2) symmetry breaking of the nucleon sea and the observed violation of the Gottfried sum rule. These effects are calculated. We obtained an excellent agreement with the experimental data in a wide range of x=[10-6,1] and Q2=[0.5,5000] GeV2 for the proton structure function. We have also calculated pion structure and compared it with the existing data. Again, the model calculations agree rather well with the data from experiment.
Quark and pion effective couplings from polarization effects
Braghin, Fabio L
2016-01-01
A flavor SU(2) effective model for pions and quarks is derived by considering polarization effects departing from the usual quark-quark effective interaction induced by dressed gluon exchange, i.e. a global color model for QCD. For that, the quark field is decomposed into a component that yields light mesons and the quark-antiquark condensate, being integrated out by means of the auxiliary field method, and another component which yields constituent quarks. Within a longwavelength and weak quark field expansion (or large quark effective mass expansion) of a quark determinant, the leading terms are found up to the second order in a zero order derivative expansion, by neglecting vector mesons that are considerably heavier than the pion. Pions are considered in the structureless limit and, besides the chiral invariant pion self interaction terms that reproduce previously derived expressions, symmetry breaking terms are also presented. The leading chiral quark-quark effective couplings are also found correspondin...
B¯s→K semileptonic decay from an Omnès improved constituent quark model
International Nuclear Information System (INIS)
We study the f+ form factor for the semileptonic B¯s→K+ℓ−ν¯ℓ decay in a constituent quark model. The valence quark estimate is supplemented with the contribution from the B¯⁎ pole that dominates the high q2 region. We use a multiply-subtracted Omnès dispersion relation to extend the quark model predictions from its region of applicability near qmax2=(MBs−MK)2∼23.75 GeV2 to all q2 values accessible in the physical decay. To better constrain the dependence of f+ on q2, we fit the subtraction constants to a combined input from previous light cone sum rule by Duplancic and Melic (2008) [11] and the present quark model results. From this analysis, we obtain Γ(B¯s→K+ℓ−ν¯ℓ)=(5.47−0.46+0.54)|Vub|2×10−9 MeV, which is about 10% and 20% higher than the predictions based on Lattice QCD and QCD light cone sum rules respectively. The former predictions, for both the form factor f+(q2) and the differential decay width, lie within the 1σ band of our estimated uncertainties for all q2 values accessible in the physical decay, except for a quite small region very close to qmax2. Differences with the light cone sum results for the form factor f+ are larger than 20% in the region above q2=15 GeV2
B-decays and B- antiB mixing within a heavy-light chiral quark model
Eeg, J O
2003-01-01
We describe a recently developed heavy-light chiral quark model and show how it can be used to calculate decay amplitudes for heavy mesons. In particular, we discuss B- antiB mixing, B -> D antiD, B -> D eta' and the beta term for D* -> D gamma .
The chiral condensate from lattice QCD with Wilson twisted mass quarks
Energy Technology Data Exchange (ETDEWEB)
Urbach, Carsten
2014-07-01
Lattice QCD is a very computer time demanding scientific application. Only with the computer time made available on supercomputers like SuperMUC significant progress, like the one reported here, can be reached. We are continuing to evaluate the data produced in this project with the focus on topological properties of QCD. Here we confront the computation of pseudo-scalar flavour singlet meson masses in 2+1+1 flavour QCD with the topological susceptibility in the so-called quenched approximation. The connection is provided by the famous Witten-Veneziano formula, which we are going to check non-perturbatively. Moreover, the computing resources made available by LRZ are used to reduce the systematic uncertainties in our results even further: in another project we are generating ensembles with physical values of the quark masses, such that a chiral extrapolation is not needed anymore. (orig.)
Chiral symmetry breaking and quark confinement in the nilpotency expansion of QCD
Caracciolo, Sergio
2010-01-01
We apply to lattice QCD a bosonization method previously developed in which dynamical bosons are generated by time-dependent Bogoliubov transformations. The transformed action can be studied by an expansion in the inverse of the nilpotency index, which is the number of fermionic states in the structure function of composite bosons. When this number diverges the model is solved by the saddle point method which has a variational interpretation. We give a stationary covariant solution for a background matter field whose fluctuations describe mesons. In the saddle point approximations live fermionic quasiparticles with quark quantum numbers which are confined, in the sense that they propagate only in pointlike color singlets. Conditions for chiral symmetry breaking are determined, to be studied numerically, and a derivation of mesons-nucleons action is outlined.
The nonlocal chiral quark model and the muon g - 2 problem
Dorokhov, A. E.; Radzhabov, A. E.; Shamakhov, F. A.; Zhevlakov, A. S.
2016-05-01
In the first part of the review we discuss the effective nonlocal approach in the quantum field theory. It concerns primary the historical retrospective of this approach, and than we concentrate on the interaction of matter particles (fermions and bosons) with the (abelian and nonabelian) gauge fields. In the second part of the review we consider the hadronic corrections (vacuum polarization) to the anomalous magnetic moment of the muon g - 2 factor discussed within the SUf(2) nonlocal chiral quark model. This is considered in the leading and, partially, in the next-to-leading orders (the effect of the fermion propagator dressing due to pion field) of expansion in small parameter 1/ N c ( N c is the number of colors in QCD).
The chiral phase transition for lattice QCD with 2 color-sextet quarks
Kogut, J. B.; Sinclair, D. K.
2015-09-01
QCD with 2 flavors of massless color-sextet quarks is studied as a possible walking-Technicolor candidate. We simulate the lattice version of this model at finite temperatures near to the chiral-symmetry restoration transition, to determine whether it is indeed a walking theory (QCD-like with a running coupling which evolves slowly over an appreciable range of length scales) or if it has an infrared fixed point, making it a conformal field theory. The lattice spacing at this transition is decreased towards zero by increasing the number Nt of lattice sites in the temporal direction. Our simulations are performed at Nt=4 ,6 ,8 ,12 , on lattices with spatial extent much larger than the temporal extent. A range of small fermion masses is chosen to make predictions for the chiral (zero mass) limit. We find that the bare lattice coupling does decrease as the lattice spacing is decreased. However, it decreases more slowly than would be predicted by asymptotic freedom. We discuss whether this means that the coupling is approaching a finite value as lattice Nt is increased—the conformal option, or if the apparent disagreement with the scaling predicted by asymptotic freedom is because the lattice coupling is a poor expansion parameter, and the theory walks. Currently, evidence favors QCD with 2 color-sextet quarks being a conformal field theory. Other potential sources of disagreement with the walking hypothesis are also discussed. We also report an estimate of the position of the deconfinement transition for Nt=12 , needed for choosing parameters for zero-temperature simulations.
Institute of Scientific and Technical Information of China (English)
PENG Jin-Song; ZHOU Li-Juan; MENG Cheng-Ju; PAN Ji-Huan; MA Wei-Xing; YUAN Tong-Quan
2013-01-01
Based on the fully dressed quark propagator and chiral perturbation theory,we study the ratio of the strange quark mass ms to up or down quark mass mu,d.The ratio is related to the determination of quark masses which are fundamental input parameters of QCD Lagrangian in the Standard Model of particle physics and can not be directly measured since the quark is confined within a hadron.An accurate determination of these QCD free parameters is extremely important for both phenomenological and theoretical applications.We begin with a brief introduction to the non-perturbation QCD theory,and then study the mass ratio in the framework of the chiral perturbation theory (xPT) with a parameterized fully dressed quark propagator which describes confining fully dressed quark propagation and is analytic everywhere in the finite complex p2-plane and has no Lehmann representation so there are no quark production thresholds in any theoretical calculations of observable data.Our prediction for the ratio ms/mu,d is consistent with other model predictions such as Lattice QCD,instanton model,QCD sum rules and the empirical values used widely in the literature.As a by-product of this study,our theoretical results,together with other predictions of physical quantities that used this quark propagator in our previous publications,clearly show that the parameterized form of the fully dressed quark propagator is an applicable and reliable approximation to the solution of the Dyson-Schwinger Equation of quark propagator in the QCD.
Relativistic effects on the neutron charge form factor in the constituent quark model
Cardarelli, F
1999-01-01
The neutron charge form factor GEn(Q**2) is investigated within a constituent quark model formulated on the light-front. It is shown that, if the quark initial motion is neglected in the Melosh rotations, the Dirac neutron form factor F1n(Q**2) receives a relativistic correction which cancels exactly against the Foldy term in GEn(Q**2), as it has been recently argued by Isgur. Moreover, at the same level of approximation the ratio of the proton to neutron magnetic form factors GMp(Q**2)/GMn(Q**2) is still given by the naive SU(6)-symmetry expectation, -3/2. However, it is also shown that the full Melosh rotations break SU(6) symmetry, giving rise to GEn(Q**2) neq 0 and GMp(Q**2)/GMn(Q**2) neq -3/2 even when a SU(6)-symmetric canonical wave function is assumed. It turns out that relativistic effects alone cannot explain simultaneously the experimental data on GEn(Q**2) and GMp(Q**2)/GMn(Q**2).
The chiral phase transition for lattice QCD with 2 colour-sextet quarks
Kogut, J B
2015-01-01
QCD with 2 flavours of massless colour-sextet quarks is studied as a possible walking-Technicolor candidate. We simulate the lattice version of this model at finite temperatures near to the chiral-symmetry restoration transition, to determine whether it is indeed a walking theory (QCD-like with a running coupling which evolves slowly over an appreciable range of length scales) or if it has an infrared fixed point, making it a conformal field theory. The lattice spacing at this transition is decreased towards zero by increasing the number $N_t$ of lattice sites in the temporal direction. Our simulations are performed at $N_t=4,6,8,12$, on lattices with spatial extent much larger than the temporal extent. A range of small fermion masses is chosen to make predictions for the chiral (zero mass) limit. We find that the bare lattice coupling does decrease as the lattice spacing is decreased. However, it decreases more slowly than would be predicted by asymptotic freedom. We discuss whether this means that the coupl...
Properties of single cluster structure of $d^*(2380)$ in chiral SU(3) quark model
Lü, Qi-Fang; Dong, Yu-Bing; Shen, Peng-Nian; Zhang, Zong-Ye
2016-01-01
The structure of $d^*(2380)$ is re-studied with the single cluster structure in the chiral SU(3) quark model which has successfully been employed to explain the scattering and binding behaviors of baryonic systems. The mass and width are explicitly calculated with two types of trial wave functions. The result shows that the $(0s)^6 [6]_{orb}$ configuration is easy to convert to the configuration with the same $[6]_{orb}$ symmetry but $2\\hbar \\omega$ excitation back and forth, however, it is seldom to turn into a two-cluster configuration with a (1s) relative motion in between. The resultant mass and width are about $2394$MeV and $25$MeV, respectively, and the stable size is about $0.75fm$, which are consistent with both the results in the two-cluster configuration calculation and the data measured by the COSY collaboration. It seems that the observed $d^*$ is a six-quark dominated exotic state with a spherical shape and breath mode in the coordinate space. Moreover, if $d^*$ does have $2\\hbar \\omega$ excitati...
The chiral quark condensate and pion decay constant in nuclear matter at next-to-leading order
Lacour, A; Meißner, U -G
2010-01-01
Making use of the recently developed chiral power counting for the physics of nuclear matter [1,2], we evaluate the in-medium chiral quark condensate up to next-to-leading order for both symmetric nuclear matter and neutron matter. Our calculation includes the full in-medium iteration of the leading order local and one-pion exchange nucleon-nucleon interactions. Interestingly, we find a cancellation between the contributions stemming from the quark mass dependence of the nucleon mass appearing in the in-medium nucleon-nucleon interactions. Only the contributions originating from the explicit quark mass dependence of the pion mass survive. This cancellation is the reason of previous observations concerning the dominant role of the long-range pion contributions and the suppression of short-range nucleon-nucleon interactions. We find that the linear density contribution to the in-medium chiral quark condensate is only slightly modified for pure neutron matter by the nucleon-nucleon interactions. For symmetric nu...
Pentaquark Θ+, constituent quark structures, and prediction of charmed Θc0 and bottomed Θb+
International Nuclear Information System (INIS)
The newly observed Θ+ resonance is believed to be a pentaquark with the constituent quarks uudds-bar. There are a few options for the constituent quark structure. Some advocate diquark-diquark-antiquark (ud)-(ud)-s-bar while others favor diquark-triquark (ud)-(uds-bar) structure. We use the color-spin hyperfine interaction to examine the energy levels of these structures, and we find that the diquark-diquark-antiquark structure is slightly favored. We proceed to write down the flavor triplet and antisextet of the charmed or bottomed exotic baryons with internal qqqqQ-bar quarks. We also estimate the mass of Θc0 and Θb+
International Nuclear Information System (INIS)
We describe the basic formulation of the parametrization scheme for the instantaneous nonlocal chiral quark model in the three-flavor case. We choose to discuss the Gaussian, Lorentzian-type, Woods-Saxon and sharp cutoff (NJL) functional forms of the momentum dependence for the form factor of the separable interaction. The four parameters: light and strange quark masses, coupling strength (GS) and range of the interaction (Λ) have been fixed by the same phenomenological inputs: pion and kaon masses, pion decay constant and light quark mass in vacuum. The Woods-Saxon and Lorentzian-type form factors are suitable for an interpolation between sharp cutoff and soft momentum dependence. Results are tabulated for applications in models of hadron structure and quark matter at finite temperatures and chemical potentials where separable models have been proven successfully
Expectation values of four-quark operators in the nucleon
Drukarev, E. G.; Ryskin, M. G.; Sadovnikova, V. A.; Lyubovitskij, V. E.; Gutsche, Th.; Faessler, Amand
2003-01-01
We calculate expectation values of QCD operators consisting of the products of the four operators of the light quarks corresponding to the scalar, pseudoscalar, vector, pseudovector (axial) and tensor Lorentz structures in the nucleon. All combinations of the light flavors are considered. For the evaluation we use elements of the Perturbative Chiral Quark Model (PCQM), approximating the contribution of the valence quarks by the contribution of the PCQM constituent quarks. The contribution of ...
Energy Technology Data Exchange (ETDEWEB)
Alexandru, Andrei [George Washington University, Washington, DC (United States); Horváth, Ivan [University of Kentucky, Lexington, KY, USA (the speaker) (United States)
2016-01-22
The validity of recently proposed equivalence between valence spontaneous chiral symmetry breaking (vSChSB) and chiral polarization of low energy Dirac spectrum (ChP) in SU(3) gauge theory, is examined for the case of twelve mass–degenerate fundamental quark flavors. We find that the vSChSB–ChP correspondence holds for regularized systems studied. Moreover, our results suggest that vSChSB occurs in two qualitatively different circumstances: there is a quark mass m{sub c} such that for m > m{sub c} the mode condensing Dirac spectrum exhibits standard monotonically increasing density, while for m{sub ch} < m < m{sub c} the peak around zero separates from the bulk of the spectrum, with density showing a pronounced depletion at intermediate scales. Valence chiral symmetry restoration may occur at yet smaller masses m < m{sub ch}, but this has not yet been seen by overlap valence probe, leaving the m{sub ch} = 0 possibility open. The latter option could place massless N{sub f}=12 theory outside of conformal window. Anomalous behavior of overlap Dirac spectrum for m{sub ch} < m < m{sub c} is qualitatively similar to one observed previously in zero and few–flavor theories as an effect of thermal agitation.
Abu-Shady, M
2015-01-01
The chiral symmetry breaking in the presence of external magnetic field is studied in the framework of logarithmic quark-sigma model. The effective logarithmic mesonic potential is employed and is numerically solved in the mean-field approximation. We find that the chiral symmetry breaking enhances in comparison with the original sigma model. Two sets of parameterization are investigated in the present model. We find that increasing coupling constant enhances the breaking symmetry while increasing sigma mass inhibits enhancing chiral broken vacuum state. A comparison with the Numbu-Jona-Lasinio model and the Schwinger-Dyson equation is discussed. We conclude that the logarithmic sigma model enhances the magnetic catalysis in comparison with the original sigma model and other models.
International Nuclear Information System (INIS)
We present many varied chiral symmetry models at the quark level which consistently describe strong interaction hadron dynamics. The pattern that emerges is a nonstrange current quark mass scale mcur ≅ (34-69) MeV and a current quark mass ratio (ms/m)cur ≅ 5-6 along with no strange quark content in nucleons. (orig./WL)
Charm-strange baryon strong decays in a chiral quark model
Liu, Lei-Hua; Zhong, Xian-Hui
2012-01-01
The strong decays of charm-strange baryons up to N=2 shell are studied in a chiral quark model. The theoretical predictions for the well determined charm-strange baryons, $\\Xi_c^*(2645)$, $\\Xi_c(2790)$ and $\\Xi_c(2815)$, are in good agreement with the experimental data. This model is also extended to analyze the strong decays of the other newly observed charm-strange baryons $\\Xi_c(2930)$, $\\Xi_c(2980)$, $\\Xi_c(3055)$, $\\Xi_c(3080)$ and $\\Xi_c(3123)$. Our predictions are given as follows. (i) $\\Xi_c(2930)$ might be the first $P$-wave excitation of $\\Xi_c'$ with $J^P=1/2^-$, favors the $|\\Xi_c'\\ ^2P_\\lambda 1/2^->$ or $|\\Xi_c'\\ ^4P_\\lambda 1/2^->$ state. (ii) $\\Xi_c(2980)$ might correspond to two overlapping $P$-wave states $|\\Xi_c'\\ ^2P_\\rho 1/2^->$ and $|\\Xi_c'\\ ^2P_\\rho 3/2^->$, respectively. The $\\Xi_c(2980)$ observed in the $\\Lambda_c^+\\bar{K}\\pi$ final state is most likely to be the $|\\Xi_c'\\ ^2P_\\rho 1/2^->$ state, while the narrower resonance with a mass $m\\simeq 2.97$ GeV observed in the $\\Xi_c^*(2645...
Structures of（ΩΩ）0＋and（[1]Ω）1＋in Extended Chiral SU（3） Quark Model
Institute of Scientific and Technical Information of China (English)
ZHANGZong-Ye; YUYou-Wen; DAILian-Rong
2003-01-01
The structures of (ΩΩ)0+ and ([1]Ω)1+ are studied in the extended chiral SU(3) quark model in which vector meson exchanges are included. The effect from the vector meson fields is very similar to that from the one-gluon exchange (OGE) interaction. Both in the chiral SU(3) quark model and in the extended chiral SU(3) quark model,di-omega (ΩΩ)0+ is always deeply bound, with over one hundred MeV binding energy, and ([1]Ω)1+ 's binding energy is around 20 MeV. An analysis shows that the quark exchange effect plays a very important role for making di-omega (ΩΩ)0+ deeply bound.
Nucleon Form Factors and N-△ Transitions in a Hypercentral Constituent Quark Model with Meson Cloud
Institute of Scientific and Technical Information of China (English)
CHEN Dina-Yong; DONG Yu-Bing
2007-01-01
We study the nucleon form factors and the nucleon-△(1232) transitions in a framework of hypercentral constituent quark model. The pion meson cloud effect is taken into account explicitly. Our results show that the pion cloud contributes substantially to the nucleon form factors as well as to the helicity amplitudes of △(1232), and it gives an improved agreement compared to the experimental measurement.
Non-leptonic decays of K-mesons within the chiral quark model
Energy Technology Data Exchange (ETDEWEB)
Bergan, A.E.
1996-12-31
This theses is based upon four previously printed paper. The main result of the first paper was that a very small contribution to K{sup o}-anti K{sup o} was found for the siamese penguin diagram with a momentum dependent penguin coefficient. The calculation was done with different regularizations. The same momentum dependent penguin interaction was used in the second paper. Dimensional regularization made it possible to calculate analytical results for K{yields}{phi}, and a relatively small g{sub 8}{sup 1/2} factor was found due to large subleading terms. In the third paper nonperturbative effects on the B{sub K} parameter were obtained. To order (G{sup 3}) a vanishing result appeared due to a complete cancellation among the 20 contributing diagrams. In the fourth paper a calculation was made of K{yields}{phi} which included non-diagonal self-energy effects due to the s{yields}d transition. This calculation made it possible to include a heavy top quark. The calculation was done in two ways. First the unphysical K{yields}{phi} transition was calculated. The result was then related to the physical K{yields}2{phi} decay due to chiral symmetry. Then the same result was obtained by a direct calculation of K{yields}2{phi}. In the CP-conserving case the contribution was small while the CP-violating part was sizable. Due to a large cancellation between the operator Q{sub 6} and Q{sub 8} the contribution was of the same size as {epsilon}/{epsilon} itself. 76 refs.
Mishra, H
2001-01-01
We discuss in this note simultaneous existence of chiral symmetry breaking and color superconductivity at finite temperature and density in a Nambu-Jona-Lasinio type model. The methodology involves an explicit construction of a variational ground state and minimisation of the thermodynamic potential. There exist nontrivial solutions to the gap equations at finite densities with both quark-antiquark as well as diquark condensates for the 'ground' state. However, such a phase is thermodynamically unstable with the pressure being negative in this region. We also compute the equation of state, and obtain the structure of the phase diagram in the model.
Chiral soliton model vs. pentaquark structure for (1540)
Indian Academy of Sciences (India)
R Ramachandran
2005-09-01
The exotic baryon + (1540 MeV) is visualized as an expected (iso) rotational excitation in the chiral soliton model. It is also argued as a pentaquark baryon state in a constituent quark model with strong diquark correlations. I contrast these two points of view; observe the similarities and differences between the two pictures. Collective excitation, the characteristic of chiral soliton model, points toward small mixing of representations in the wake of (3) breaking. In contrast, constituent quark models prefer near `ideal' mixing, similar to - mixing.
Singha, Subhash
2016-01-01
We studied the number of constituent quark scaling (NCQ) behaviour of elliptic flow ($v_{2}$) under the framework of A Multi-Phase Transport model (AMPT) at both top-RHIC and LHC energies. The NCQ-scaling in $v_{2}$ holds at top-RHIC energy with AMPT string melting version, while it breaks in Pb+Pb collisions at LHC energy using the same framework. The breaking of NCQ-scaling at LHC energy has been studied by varying the magnitude of parton-parton scattering cross-section and lifetime of hadronic cascade as implemented in AMPT. We find that the breaking of NCQ scaling in Pb+Pb collisions at $\\sqrt{s_{NN}}$ =2.76 TeV is independent of the magnitude of parton-parton cross-section and the later stage hadronic interactions. Further we observed that scaling holds in a small collision system like Si+Si at $\\sqrt{s_{NN}}$ = 2.76 TeV. We discussed that the breaking of NCQ scaling is possibly due to high phase-space density of constituents quarks in Pb+Pb collisions at $\\sqrt{s_{NN}}$ = 2.76 TeV.
Blanco, L. A.; Bonnaz, R.; Silvestre-Brac, B.; Fernandez, F; Valcarce, A.
2001-01-01
The classical van Royen-Weisskopf formula for the decay width of a meson into a lepton-antilepton pair is modified in order to include non-zero quark momentum contributions within the meson as well as relativistic effects. Besides, a phenomenological electromagnetic density for quarks is introduced. The meson wave functions are obtained from two different models: a chiral constituent quark model and a quark potential model including instanton effects. The modified van Royen-Weisskopf formula ...
Masses of charm and beauty baryons in the constituent quark model
International Nuclear Information System (INIS)
The masses of the ground state heavy baryons are studied using the hypercentral approach. The considered potential is a combination of Coulombic, linear confining and harmonic oscillator terms. An improved form of the hyperfine interaction and isospin dependent quark potential is introduced. By solving the Schroedinger equation for three particles system, we calculate the ground state masses of the baryons containing one, two and three heavy quarks. The obtained results are very close to the ones obtained in experiments or in the other works. (author)
Charge symmetry breaking from a chiral extrapolation of moments of quark distribution functions
Shanahan, P. E.; Thomas, A. W.; Young, R.D.(ARC Centre of Excellence for Particle Physics at the Terascale and CSSM, School of Chemistry and Physics, University of Adelaide, Adelaide, SA 5005, Australia)
2013-01-01
We present a determination, from lattice QCD, of charge symmetry violation in the spin- independent and spin-dependent parton distribution functions of the nucleon. This is done by chirally extrapolating recent QCDSF/UKQCD Collaboration lattice simulations of the first several Mellin moments of the parton distribution functions of octet baryons to the physical point. We find small chiral corrections for the polarized moments, while the corrections are quantitatively significant in the unpolar...
Samart, Daris; Nualchimplee, Chakrit; Yan, Yupeng
2016-06-01
In this work we construct a chiral SU(3) Lagrangian with D mesons of spin JP=0- and JP=1- and charmed baryons of spin JP=1 /2+ and JP=3 /2+. There are 42 leading two-body counterterms involving two charmed baryon fields and two D meson fields in the constructed Lagrangian. The heavy-quark spin symmetry leads to 35 sum rules, while the large-Nc operator analysis predicts 29 at the next-to leading order of the 1 /Nc expansion. The combination of the sum rules from both the heavy-quark symmetry and the large-Nc analysis results in 38 independent sum rules, which reduces the number of free parameters in the chiral Lagrangian to only four. This is a remarkable result demonstrating the consistency of the heavy-quark symmetry and large-Nc operator analysis.
Samart, Daris; Yan, Yupeng
2016-01-01
We construct, in the work, chiral $SU(3)$ Lagrangian with $D$ mesons of spin $J^P=0^-$ and $J^P=1^-$ and charmed baryons of spin $J^P=1/2^+$ and $J^P=3/2^+$. There are 42 leading two-body counter-terms involving two charmed baryon fields and two $D$ meson fields in the constructed Lagrangian. The heavy-quark spin symmetry leads to 35 sum rules while the large-$N_c$ operator analysis predicts 29 ones at the next-to leading order of $1/N_c$ expansion. The combination of the sum rules from both the heavy-quark symmetry and the large-$N_c$ analysis results in 38 independent sum rules which reduces the number of free parameters in the chiral Lagrangian down to 4 only. This is a remarkable result demonstrating the consistency of the heavy-quark symmetry and large-$N_c$ operator analysis.
The fate of pion condensation in quark matter: from the chiral to the real world
Abuki, H; Gatto, R; Pellicoro, M; Ruggieri, M
2008-01-01
We study aspects of the pion condensation in a two-flavor neutral quark matter using the Nambu--Jona-Lasinio (NJL) model of QCD at finite density. We investigate the role of electric charge neutrality, and explicit symmetry breaking via quark mass, both of which control the onset of the charged pion $(\\pi^c)$ condensation. We show that the equality between the electric chemical potential and the in-medium pion mass, $\\mu_{e}=M_{\\pi^-}$, as a threshold, persists even for composite pion system in the medium, provided the transition to the pion condensed phase is of the second order. Moreover we find that the pion condensate in the neutral quark matter is extremely fragile to the symmetry breaking effect via a current quark mass $m$, being ruled out for $m$ larger than the order of 10 keV.
From Quarks and Gluons to Hadrons: Chiral Symmetry Breaking in Dynamical QCD
Braun, Jens; Pawlowski, Jan M; Rennecke, Fabian
2014-01-01
We present an analysis of the dynamics of two-flavour QCD in the vacuum. Special attention is payed to the transition from the high energy quark-gluon regime to the low energy regime governed by hadron dynamics. This is done within a functional renormalisation group approach to QCD amended by dynamical hadronisation techniques. The latter allow us to describe conveniently the transition from the perturbative high-energy regime to the nonperturbative low-energy limit without suffering from a fine-tuning of model parameters. In the present work, we apply these techniques to two-flavour QCD with physical quark masses and show how the dynamics of the dominant low-energy degrees of freedom emerge from the underlying quark-gluon dynamics.
From quarks and gluons to hadrons: Chiral symmetry breaking in dynamical QCD
Braun, Jens; Fister, Leonard; Pawlowski, Jan M.; Rennecke, Fabian
2016-08-01
We present an analysis of the dynamics of two-flavor QCD in the vacuum. Special attention is paid to the transition from the high-energy quark-gluon regime to the low-energy regime governed by hadron dynamics. This is done within a functional renormalization group approach to QCD amended by dynamical hadronization techniques. These techniques allow us to describe conveniently the transition from the perturbative high-energy regime to the nonperturbative low-energy limit without suffering from a fine-tuning of model parameters. In the present work, we apply these techniques to two-flavor QCD with physical quark masses and show how the dynamics of the dominant low-energy degrees of freedom emerge from the underlying quark-gluon dynamics.
Capdevilla, R. M.; Doff, A.(Universidade Tecnológica Federal do Paraná – UTFPR – DAFIS, Av. Monteiro Lobato Km 04, 84016-210 Ponta Grossa, PR, Brazil); Natale, A. A.
2015-01-01
Considering a QCD chiral symmetry breaking model where the gap equation contains an effective confining propagator and a dressed gluon propagator with a dynamically generated mass, we verify that the chiral symmetry is restored for a large number of quarks $n_{f}\\approx 7-13$. We discuss the uncertainty in the results, that is related to the determination of the string tension ($K_{F}$), appearing in the confining propagator, and the effective gluon mass ($m_{g}$) at large $n_{f}$.
The pion-nucleon Σ-term in a chiral quark model
International Nuclear Information System (INIS)
The pion/nucleon Σ-term is calculated in a linear σ-model based on the U(3) x U(3) quark effective Lagrangian. The importance of the pole diagram with the scalar meson f0(400 - 1200) is demonstrated. For the mass of this meson the value 400 MeV was chosen, which corresponds to the theoretical predictions taking into account singlet-octet mixing of scalar isoscalar mesons and glueball on the one hand and to recent experimental data on the other. The resulting value σ = 75 MeV is in agreement with the latest analysis of experimental data on the π-N scattering. It is shown that the hypothesis of the content of strange quarks in the valence structure of a nucleon is not necessary to reach agreement with experimental data. (Authors)
Probing b-quark charged-current chiral structure via polarized-Λb semileptonic decay
International Nuclear Information System (INIS)
Λb semileptonic decay to Λce anti νe ist studied within the heavy quark effective theory, where Λb is moving and polarized along the direction of its motion. Normalized energy distributions of e and Λc are both calculated for V±A interactions by taking the OMIKRON ( anti Λ/mc) ( anti Λ triple bond mΛc-mc) corrections and electron pt cut effects into account. It is shown that the form factor (Isgur-Wise function) effects are significant: The shapes of the distribution curves are thereby considerably changed in comparison with those calculated within the quark model. In case of the electron energy spectrums, the difference between the V±A interactions are enhanced, while that in the Λc energy spectrums decreases. On the other hand, the OMIKRON ( anti Λ/mc) corrections are found to be negligible in both spectrums. (orig.)
Initial nucleon structure results with chiral quarks at the physical point
Syritsyn, S; Engelhardt, M; Green, J; Izubuchi, T; Jung, C; Krieg, S; Lin, M; Meinel, S; Negele, J; Ohta, S; Pochinsky, A; Shintani, E
2014-01-01
We report initial nucleon structure results computed on lattices with 2+1 dynamical M\\"obius domain wall fermions at the physical point generated by the RBC and UKQCD collaborations. At this stage, we evaluate only connected quark contributions. In particular, we discuss the nucleon vector and axial-vector form factors, nucleon axial charge and the isovector quark momentum fraction. From currently available statistics, we estimate the stochastic accuracy of the determination of $g_A$ and $_{u-d}$ to be around 10%, and we expect to reduce that to 5% within the next year. To reduce the computational cost of our calculations, we extensively use acceleration techniques such as low-eigenmode deflation and all-mode-averaging (AMA). We present a method for choosing optimal AMA parameters.
From Quarks and Gluons to Hadrons: Chiral Symmetry Breaking in Dynamical QCD
Braun, Jens; Fister, Leonard; Pawlowski, Jan M; Rennecke, Fabian
2016-01-01
We present an analysis of the dynamics of two-flavour QCD in the vacuum. Special attention is payed to the transition from the high energy quark-gluon regime to the low energy regime governed by hadron dynamics. This is done within a functional renormalisation group approach to QCD amended by dynamical hadronisation techniques. The latter allow us to describe conveniently the transition from the perturbative high-energy regime to the nonperturbative low-energy limit without suffering from a f...
B_s-\\bar{B_s} mixing with a chiral light quark action
Becirevic, D; Boucaud, P; Leroy, J P; Le Yaouanc, A; Pène, O; Boucaud, Ph.
2005-01-01
We study the $B^0_s-\\bar{B^0_s}$ mixing amplitude in Standard Model by computing the relevant hadronic matrix element in the static limit of lattice HQET with the Neuberger light quark action. In the quenched approximation, and after matching to the $\\bar{\\rm MS}$ scheme in QCD, we obtain $B^{\\bar{\\rm MS}}_{B_s}(m_b)=0.940(16)(22)$.
The effect of the Polyakov loop on the chiral phase transition
Szép Zs.; Markó G.
2010-01-01
The Polyakov loop is included in the SU(2)_L x SU(2)_R chiral quark-meson model by considering the propagation of the constituent quarks, coupled to the (sigma,pi) meson multiplet, on the homogeneous background of a temporal gauge field, diagonal in color space. The model is solved at finite temperature and quark baryon chemical potential both in the chiral limit and for the physical value of the pion mass by using an expansion in the number of flavors N_f. Keeping the fermion propagator at i...
Bonanno, Luca; Lavagno, Andrea
2007-01-01
We discuss two models for describing the behavior of matter at large densities and intermediate temperatures. In both models a softening of the equation of state takes place due to the appearance of new degrees of freedom. The first is an hadronic model in which the softening is due to chiral symmetry restoration. In the second model the softening is associated with the formation of clusters of quarks in the mixed phase. We show that both models allow a significant softening but, in the first case the bulk modulus is mainly dependent on the density, while in the mixed phase model it also strongly depends on the temperature. We also show that the bulk modulus is not vanishing in the mixed phase due to the presence of two conserved charges, the baryon and the isospin one. Only in a small region of densities and temperatures the incompressibility becomes extremely small. Finally we compare our results with recent analysis of heavy ion collisions at intermediate energies.
String formation and chiral symmetry breaking in the heavy-light quark-antiquark system in QCD
Simonov, YA; Tjon, JA
2000-01-01
The effective quark Lagrangian is written for a light quark in the field of a static antiquark, explicitly containing field correlators as coefficient functions of products of quark operators. At large N-c the closed system of equations for the gauge-invariant quark Green's function in the field of
Baryons with Two Heavy Quarks as Solitons
Bander, Myron; Subbaraman, Anand
1994-01-01
Using the chiral soliton model and heavy quark symmetry we study baryons containing two heavy quarks. If there exists a stable (under strong interactions) meson consisting of two heavy quarks and two light ones, then we find that there always exists a state of this meson bound to a chiral soliton and to a chiral anti-soliton, corresponding to a two heavy quark baryon and a baryon containing two heavy anti-quarks and five light quarks, or a ``heptaquark".
Intrinsic transverse momentum and dynamical chiral symmetry breaking
Energy Technology Data Exchange (ETDEWEB)
Christian Weiss, Peter Schweitzer, Mark Strikman
2013-01-01
We study the effect of QCD vacuum structure on the intrinsic transverse momentum distribution of partons in the nucleon at a low scale. The dynamical breaking of chiral symmetry is caused by non-perturbative interactions at distances of the order rho ~ 0.2 - 0.3 fm, much smaller than the typical nucleon size R ~ 1 fm, resulting in a two-scale picture of nucleon structure. Using an effective dynamical model based on chiral constituent quark degrees of freedom and the 1/N_c expansion (chiral quark-soliton model), we calculate the transverse momentum distribution of quarks and antiquarks at a low scale. The distribution of valence quarks is localized at p_T ~ 1/R. The distribution of flavor-singlet unpolarized sea quarks exhibits a power-like tail extending up to the chiral-symmetry-breaking scale 1/{rho}. A similar tail is present in the flavor-nonsinglet polarized sea. These features are model-independent and represent the imprint of the QCD vacuum on the nucleon's partonic structure. At the level of the nucleon's light-cone wave function, we show that sea quarks partly exist in correlated pairs of transverse size {rho} << R, analogous to short-range NN correlations in nuclei. We discuss the implications of our findings for the transverse momentum distributions in hard scattering processes (semi-inclusive DIS, Drell-Yan pair production) and possible experimental tests of the non-perturbative parton correlations induced by QCD vacuum structure.
Quark Mass Dependence of Nucleon Magnetic Moment and Charge Radii
Institute of Scientific and Technical Information of China (English)
MA Wei-Xing; ZHOU Li-Juan; GU Yun-Ting; PING Rong-Gang
2005-01-01
Understanding hadron structure within the framework of QCD is an extremely challenging problem. Our purpose here is to explain the model-independent consequences of the approximated chiral symmetry of QCD for two famous results concerning the quark structure of the nucleon. We show that both the apparent success of the constituent quark model in reproducing the ratio of proton to neutron magnetic moments and the apparent success of the Foldy term in reproducing the observed charge radius of the neutron are coincidental. That is, a relatively small change of the current quark mass would spoil both results.
Liu, Keh-Fei
2016-01-01
The relevance of chiral symmetry in baryons is highlighted in three examples in the nucleon spectroscopy and structure. The first one is the importance of chiral dynamics in understanding the Roper resonance. The second one is the role of chiral symmetry in the lattice calculation of $\\pi N \\sigma$ term and strangeness. The third one is the role of chiral $U(1)$ anomaly in the anomalous Ward identity in evaluating the quark spin and the quark orbital angular momentum. Finally, the chiral effective theory for baryons is discussed.
Quark Orbital Angular Momentum in the Baryon
Song, Xiaotong
2000-01-01
Analytical and numerical results, for the orbital and spin content carried by different quark flavors in the baryons, are given in the chiral quark model with symmetry breaking. The reduction of the quark spin, due to the spin dilution in the chiral splitting processes, is transferred into the orbital motion of quarks and antiquarks. The orbital angular momentum for each quark flavor in the proton as a function of the partition factor $\\kappa$ and the chiral splitting probability $a$ is shown...
Partial quenching and chiral symmetry breaking
Creutz, Michael
2014-01-01
Partially quenched chiral perturbation theory assumes that valence quarks propagating on gauge configurations prepared with sea quarks of different masses will form a chiral condensate as the valence quark mass goes to zero. I present a counterexample involving non-degenerate sea quarks where the valence condensate does not form.
Energy Technology Data Exchange (ETDEWEB)
Barbara Pasquini, Peter Schweitzer
2011-06-01
We present results for leading-twist azimuthal asymmetries in semi-inclusive lepton-nucleon deep-inelastic scattering due to naively time-reversal odd transverse-momentum dependent parton distribution functions from the light-cone constituent quark model. We carefully discuss the range of applicability of the model, especially with regard to positivity constraints and evolution effects. We find good agreement with available experimental data from COMPASS and HERMES, and present predictions to be tested in forthcoming experiments at Jefferson Lab.
Takahashi, Y.; Eby, P. B.
1985-01-01
Possibilities of observing abundances of phi mesons and narrow hadronic pairs, as results of QGP and Chiral transitions, are considered for nucleus-nucleus interactions. Kinematical requirements in forming close pairs are satisfied in K+K decays of S(975) and delta (980) mesons with small phi, and phi (91020) mesons with large PT, and in pi-pi decays of familiar resonance mesons only in a partially restored chiral symmetry. Gluon-gluon dominance in QGP can enhance phi meson production. High hadronization rates of primordial resonance mesons which form narrow hadronic pairs are not implausible. Past cosmic ray evidences of anomalous phi production and narrow pair abundances are considered.
Effective field theories of baryons and mesons, or, what do quarks do?
International Nuclear Information System (INIS)
This thesis is an attempt to understand the properties of the protons, pions and other hadrons in terms of their fundamental building blocks. In the first chapter the author reviews several of the approaches that have already been developed. The Nambu-Jona-Lasinio model offers the classic example of a derivation of meson properties from a quark Lagrangian. The chiral quark model encodes much of the intuition acquired in recent decades. The author also discusses the non-linear sigma model, the Skyrme model, and the constituent quark model, which is one of the oldest and most successful models. In the constituent quark model, the constituent quark appears to be different from the current quark that appears in the fundamental QCD Lagrangian. Recently it was proposed that the constituent quark is a topological soliton. In chapter 2 the author investigates this soliton, calculating its mass, radius, magnetic moment, color magnetic moment, and spin structure function. Within the approximations used, the magnetic moments and spin structure function cannot simultaneously be made to agree with the constituent quark model. In chapter 3 the author uses a different plan of attack. Rather than trying to model the constituents of the baryon, he begins with an effective field theory of baryons and mesons, with couplings and masses that are simply determined phenomenologically. Meson loop corrections to baryon axial currents are then computed in the 1/N expansion. It is already known that the one-loop corrections are suppressed by a factor 1/N; here it is shown that the two-loop corrections are suppressed by 1/N2. To leading order, these corrections are exactly the same as would be calculated in the constituent quark model. This method therefore offers a different approach to the constituent quark
Directory of Open Access Journals (Sweden)
Bijnens Johan
2016-01-01
Full Text Available This talk discusses our old work on the hadronic light-by-light contribution to the muon anomalous magnetic moment and some more recent contributions. I discuss the various contributions starting with pseudoscalar meson exchange, the quark- and pion-loop, as well as scalar and a1-exchange. For the π0-exchange I point out a possible large enhancement when only connected contributions are included. For the quark-loop I include some comments about the more recent estimates of this contribution. The pion-loop is discussed in more detail, in particular I discuss our unpublished work on including effects from a1 and the polarizability.
International Nuclear Information System (INIS)
The classical van Royen-Weisskopf formula for the decay width of a meson into a lepton-antilepton pair is modified in order to include nonzero quark momentum contributions within the meson as well as relativistic effects. Besides, a phenomenological electromagnetic density for quarks is introduced. The meson wave functions are obtained from two different models: a chiral constituent quark model and a quark potential model including instanton effects. The modified van Royen-Weisskopf formula is found to improve systematically the results for the widths, giving an overall good description of all known decays
Chiral String-Soliton Model for the light chiral baryons
Pavlovsky, Oleg
2010-01-01
The Chiral String-Soliton Model is a joining of the two notions about the light chiral baryons: the chiral soliton models (like the Skyrme model) and the Quark-Gluon String models. The ChSS model is based on the Effective Chiral Lagrangian which was proposed in [arXiv:hep-ph/0306216]. We have studied the physical properties of the light chiral baryon within the framework of this ChSS model.
Scalar-Quark Systems and Chimera Hadrons in SU(3)_c Lattice QCD
Iida, H; Takahashi, T T
2007-01-01
Light scalar-quarks \\phi (colored scalar particles or idealized diquarks) and their color-singlet hadronic states are studied with quenched SU(3)_c lattice QCD in terms of mass generation in strong interaction without chiral symmetry breaking. We investigate ``scalar-quark mesons'' \\phi^\\dagger \\phi and ``scalar-quark baryons'' \\phi\\phi\\phi which are the bound states of scalar-quarks \\phi. We also investigate the bound states of scalar-quarks \\phi and quarks \\psi, i.e., \\phi^\\dagger \\psi, \\psi\\psi\\phi and \\phi\\phi\\psi, which we name ``chimera hadrons''. All the new-type hadrons including \\phi are found to have a large mass even for zero bare scalar-quark mass m_\\phi=0 at a^{-1}\\simeq 1GeV. We find that the constituent scalar-quark and quark picture is satisfied for all the new-type hadrons. Namely, the mass of the new-type hadron composed of m \\phi's and n \\psi's, M_{{m}\\phi+{n}\\psi}, satisfies M_{{m}\\phi+{n}\\psi}\\simeq {m} M_\\phi +{n} M_\\psi, where M_\\phi and M_\\psi are the constituent scalar-quark and quark...
Silva, A; Kim, H C; Urbano, D; Goeke, Klaus; Kim, Hyun-Chul; Silva, Antonio; Urbano, Diana
2006-01-01
We investigate parity-violating electroweak asymmetries in the elastic scattering of polarized electrons off protons within the framework of the chiral quark-soliton model ($\\chi$QSM). We use as input the former results of the electromagnetic and strange form factors and newly calculated SU(3) axial-vector form factors, all evaluated with the same set of four parameters adjusted several years ago to general mesonic and baryonic properties. Based on this scheme, which yields positive electric and magnetic strange form factors with a $\\mu_s=(0.08-0.13)\\mu_N$, we determine the parity-violating asymmetries of elastic polarized electron-proton scattering. The results are in a good agreement with the data of the A4, HAPPEX, and SAMPLE experiments and reproduce the full $Q^2$-range of the G0-data. We also predict the parity-violating asymmetries for the backward G0 experiment.
Effects of (axialvector mesons on the chiral phase transition: initial results
Directory of Open Access Journals (Sweden)
Kovács P.
2014-01-01
Full Text Available We investigate the effects of (axialvector mesons on the chiral phase transition in the framework of an SU(3, (axialvector meson extended linear sigma model with additional constituent quarks and Polyakov loops. We determine the parameters of the Lagrangian at zero temperature in a hybrid approach, where we treat the mesons at tree-level, while the constituent quarks at 1-loop level. We assume two nonzero scalar condensates and together with the Polyakov-loop variables we determine their temperature dependence according to the 1-loop level field equations.
Institute of Scientific and Technical Information of China (English)
ZONG Hong-Shi; PING Jia-Lun; SUN Wei-Min; CHANG Chao-Hsi; WANG Fan
2002-01-01
We exhibit a method for obtaining the low chemical potential dependence of the dressed quark propagatorfrom an effective quark-quark interaction model. Within this approach we explore the chemical potential dependenceof the dressed-quark propagator, which provides a means of determining the behavior of the chiral and deconfinementorder parameters. A comparison with the results of previous researches is given.
Lavelle, Martin; McMullan, David
1995-01-01
It is shown that colour can only be defined on gauge invariant states. Since the ability to associate colour with constituent quarks is an integral part of the constituent quark model, this means that, if we want to extract constituent quarks from QCD, we need to dress Lagrangian quarks with gluons so that the result is gauge invariant. We further prove that gauge fixings can be used to construct such dressings. Gauge invariant dressed quark states are presented and a direct approach to the i...
Dynamics and Stability of Chiral Fluid
Mishustin, Igor N; Denicol, Gabriel S; Torrieri, Giorgio
2014-01-01
Starting from the linear sigma model with constituent quarks we derive the chiral fluid dynamics where hydrodynamic equations for the quark fluid are coupled to the equation of motion for the order-parameter field. In a static system at thermal equilibrium this model leads to a chiral phase transition which, depending on the choice of the quark-meson coupling constant, could be a crossover or a first order one. We investigate the stability of the chiral fluid in the static and expanding backgrounds by considering the evolution of perturbations with respect to the mean-field solution. In the static background the spectrum of plane-wave perturbations consists of two branches, one corresponding to the sound waves and another to the sigma-meson excitations. For large couplings these two branches "cross" and the excitation spectrum acquires exponentially growing modes. The stability analysis is also done for the Bjorken-like background solution by explicitly solving the time-dependent differential equation for per...
Duality between quark-quark and quark-antiquark pairing in 1+1 dimensional large N models
Thies, Michael
2003-01-01
We identify a canonical transformation which maps the chiral Gross-Neveu model onto a recently proposed Cooper pair model. Baryon number and axial charge are interchanged. The same physics can be described either as chiral symmetry breaking (quark-antiquark pairing) or as superconductivity (quark-quark pairing).
The chiral magnetic effect in hydrodynamical approach
Sadofyev, A. V.; Isachenkov, M. V.
2010-01-01
In quark-gluon plasma nonzero chirality can be induced by the chiral anomaly. When a magnetic field is applied to a system with nonzero chirality an electromagnetic current is induced along the magnetic field. This phenomenon is called the chiral magnetic effect. In this paper appearance of the chiral magnetic effect in hydrodynamical approximation is shown. We consider a hydrodynamical model for chiral liquid with two independent currents of left and right handed particles in the presence of...
Chiral symmetry and lattice fermions
Creutz, Michael
2013-01-01
Lattice gauge theory and chiral perturbation theory are among the primary tools for understanding non-perturbative aspects of QCD. I review several subtle and sometimes controversial issues that arise when combining these techniques. Among these are one failure of partially quenched chiral perturbation theory when the valence quarks become lighter than the average sea quark mass and a potential ambiguity in comparisons of perturbative and lattice properties of non-degenerate quarks.
A chiral quark-motivated meson model and the CP violation in K → 3π decays
International Nuclear Information System (INIS)
The Nambu-Jona-Lasinio model is introduced as an approximation of the QCD, and in section 2 from this a meson model is derived by means of the functional integration. On the basis of the effective quark model of Vainstain-Shifman-Sacharov, which describes the weak interaction of quarks, weak and electromagnetic meson currents are derived. The so obtained meson model describes strong, weak, and electromagnetic interactions of mesons. In the 3rd section K → 2π, 3π decays are studied. After an analysis of experimental data a prediction on the direct CP violation in charged K → 3π decays is made. Starting from this estimation an experiment for the measurement of the CP asymmetry of the decay K± → π±π0π0 at an existing facility at the accelerator U-70 in Serpukhov is proposed. (orig./HSI)
Electromagnetic properties of light and heavy baryons in the relativistic quark model
Energy Technology Data Exchange (ETDEWEB)
Nicmorus Marinescu, Diana
2007-06-14
within this model reveals an exact agreement in leading order with the model-independent predictions for the magnetic moments of the heavy baryons. For the light sector, a Lorentz covariant chiral quark Lagrangian is used to dress the constituent quarks by pseudoscalar meson clouds. The main achievement consists in the factorization of the valence quark contributions and the meson cloud contributions in the calculation of electromagnetic properties of light baryons. (orig.)
Electromagnetic properties of light and heavy baryons in the relativistic quark model
International Nuclear Information System (INIS)
model reveals an exact agreement in leading order with the model-independent predictions for the magnetic moments of the heavy baryons. For the light sector, a Lorentz covariant chiral quark Lagrangian is used to dress the constituent quarks by pseudoscalar meson clouds. The main achievement consists in the factorization of the valence quark contributions and the meson cloud contributions in the calculation of electromagnetic properties of light baryons. (orig.)
Catalysis of Dynamical Chiral Symmetry Breaking by Chiral Chemical Potential
Braguta, V V
2016-01-01
In this paper we study the properties of media with chiral imbalance parameterized by chiral chemical potential. It is shown that depending on the strength of interaction between constituents in the media the chiral chemical potential either creates or enhances dynamical chiral symmetry breaking. Thus the chiral chemical potential plays a role of the catalyst of dynamical chiral symmetry breaking. Physically this effect results from the appearance of the Fermi surface and additional fermion states on this surface which take part in dynamical chiral symmetry breaking. An interesting conclusion which can be drawn is that at sufficiently small temperature chiral plasma is unstable with respect to condensation of Cooper pairs and dynamical chiral symmetry breaking even for vanishingly small interactions between constituents.
The effect of the Polyakov loop on the chiral phase transition
Directory of Open Access Journals (Sweden)
Szép Zs.
2011-04-01
Full Text Available The Polyakov loop is included in the S U(2L × S U(2R chiral quark-meson model by considering the propagation of the constituent quarks, coupled to the (σ, π meson multiplet, on the homogeneous background of a temporal gauge field, diagonal in color space. The model is solved at finite temperature and quark baryon chemical potential both in the chiral limit and for the physical value of the pion mass by using an expansion in the number of flavors Nf. Keeping the fermion propagator at its tree-level, a resummation on the pion propagator is constructed which resums infinitely many orders in 1/Nf, where O(1/Nf represents the order at which the fermions start to contribute in the pion propagator. The influence of the Polyakov loop on the tricritical or the critical point in the µq – T phase diagram is studied for various forms of the Polyakov loop potential.
The effect of the Polyakov loop on the chiral phase transition
Markó, G.; Szép, Zs.
2011-04-01
The Polyakov loop is included in the S U(2)L × S U(2)R chiral quark-meson model by considering the propagation of the constituent quarks, coupled to the (σ, π) meson multiplet, on the homogeneous background of a temporal gauge field, diagonal in color space. The model is solved at finite temperature and quark baryon chemical potential both in the chiral limit and for the physical value of the pion mass by using an expansion in the number of flavors Nf. Keeping the fermion propagator at its tree-level, a resummation on the pion propagator is constructed which resums infinitely many orders in 1/Nf, where O(1/Nf) represents the order at which the fermions start to contribute in the pion propagator. The influence of the Polyakov loop on the tricritical or the critical point in the µq - T phase diagram is studied for various forms of the Polyakov loop potential.
International Nuclear Information System (INIS)
The formation and evolution of the elliptic flow pattern in Pb+Pb collisions at √(s)=5.5A TeV and in Au+Au collisions at √(s)=200A GeV are analyzed for different hadron species within the framework of the HYDJET++ Monte Carlo model. The model contains both hydrodynamic state and jets, thus allowing for a study of the interplay between the soft and hard processes. It is found that jets terminate the rise of the elliptic flow with increasing transverse momentum. Since jets are more influential at the Large Hadron Collider (LHC) than at the Relativistic Heavy Ion Collider (RHIC), the elliptic flow at LHC should be weaker than that at RHIC. The influence of resonance decays on particle elliptic flow is also investigated. These final state interactions enhance the low-pT part of the v2 of pions and light baryons and work toward the fulfillment of idealized constituent quark scaling.
Kojo, Toru; McLerran, Larry; Pisarski, Robert D
2009-01-01
We consider the formation of chiral density waves in Quarkyonic matter, which is a phase where cold, dense quarks experience confining forces. We model confinement following Gribov and Zwanziger, taking the gluon propagator, in Coulomb gauge and momentum space, as 1/(p^2)^2. We assume that the number of colors, N, is large, and that the quark chemical potential, mu, is much larger than renormalization mass scale, Lambda_QCD. To leading order in 1/N and Lambda_QCD, a gauge theory with Nf flavors of massless quarks in 3+1 dimensions naturally reduces to a gauge theory in 1+1 dimensions, with an enlarged flavor symmetry of SU(2Nf). Through an anomalous chiral rotation, in two dimensions a Fermi sea of massless quarks maps directly onto the corresponding theory in vacuum. A chiral condensate forms locally, and varies with the spatial position, z, as . Following Schon and Thies, we term this two dimensional pion condensate a (Quarkyonic) chiral spiral. Massive quarks also exhibit chiral spirals, with the magnitude...
Kalaydzhyan, Tigran
2014-01-01
We argue that the strongly coupled quark-gluon plasma formed at LHC and RHIC can be considered as a chiral superfluid. The "normal" component of the fluid is the thermalized matter in common sense, while the "superfluid" part consists of long wavelength (chiral) fermionic states moving independently. We use the bosonization procedure with a finite cut-off and obtain a dynamical axion-like field out of the chiral fermionic modes. Then we use relativistic hydrodynamics for macroscopic description of the effective theory obtained after the bosonization. Finally, solving the hydrodynamic equations in gradient expansion, we find that in the presence of external electromagnetic fields or rotation the motion of the "superfluid" component gives rise to the chiral magnetic, chiral vortical, chiral electric and dipole wave effects. Latter two effects are specific for a two-component fluid, which provides us with crucial experimental tests of the model.
Directory of Open Access Journals (Sweden)
Goldstein Gary R.
2015-01-01
Full Text Available Nucleon spin structure, transversity and the tensor charge are of central importance to understanding the role of QCD in hadronic physics. A new approach to measuring orbital angular momenta of quarks in the proton via twist 3 GPDs is shown. The “flexible parametrization” of chiral even GPDs is reviewed and its transformation into the chiral odd sector is discussed. The resulting parametrization is applied to recent data on π0 and η electroproduction.
Chiral measurements with the Fixed-Point Dirac operator and construction of chiral currents
International Nuclear Information System (INIS)
In this preliminary study, we examine the chiral properties of the parametrized Fixed-Point Dirac operator DFP, see how to improve its chirality via the Overlap construction, measure the renormalized quark condensate Σ-circumflex and the topological susceptibility χt, and investigate local chirality of near zero modes of the Dirac operator. We also give a general construction of chiral currents and densities for chiral lattice actions
Role of five-quark components in radiative and strong decays of the Λ(1405) resonance
International Nuclear Information System (INIS)
Within an extended chiral constituent quark model, the three- and five-quark structure of the S01 resonance Λ(1405) is investigated. Helicity amplitudes for electromagnetic decays [Λ(1405)→Λ(1116)γ, Σ(1194)γ] and transition amplitudes for strong decays [Λ(1405)→Σ(1194)π, K-p] are derived, as well as the relevant decay widths. The experimental value for the strong decay width, ΓΛ(1405)→(Σπ)o =50±2 MeV, is well reproduced with about 50% of a five-quark admixture in the Λ(1405). Important effects owing to the configuration mixing among Λ12PA, Λ82PM, and Λ84PM are found. In addition, transitions between the three- and the five-quark components in the baryons turn out to be significant in both radiative and strong decays of the Λ(1405) resonance.
Effects of isovecter coupling on quark matter properties in NJL model
Liu, He; Chen, Lie-Wen; Sun, Kai-Jia
2016-01-01
We have studied the properties of hot and dense quark matter based on the 3-flavor Nambu-Jona-Lasinio model as well as its Polyakov-loop extension with scalar-isovector and vector-isovector couplings. Isospin splittings of constituent mass, chiral phase transition boundary, and critical point for $u$ and $d$ quarks have been observed for positive isovector coupling constants but are suppressed for negative ones. The quark matter symmetry energy is shown to be sensitive to the isovector coupling. A positive scalar-isovector coupling constant is more likely to lead to an unstable equation of state for isospin asymmetric quark matter. The isovector coupling has been further found to affect particle fractions as well as the equation of state in hybrid stars.
Overlap Quark Propagator in Coulomb Gauge QCD
Mercado, Ydalia Delgado; Schröck, Mario
2014-01-01
The chirally symmetric Overlap quark propagator is explored in Coulomb gauge. This gauge is well suited for studying the relation between confinement and chiral symmetry breaking, since confinement can be attributed to the infrared divergent Lorentz-vector dressing function. Using quenched gauge field configurations on a $20^4$ lattice, the quark propagator dressing functions are evaluated, the dynamical quark mass is extracted and the chiral limit of these quantities is discussed. By removing the low-lying modes of the Dirac operator, chiral symmetry is artificially restored. Its effect on the dressing functions is discussed.
About chiral models of dense matter and its magnetic properties
International Nuclear Information System (INIS)
The chiral models of dense nucleon matter are discussed. The quark matter with broken chiral symmetry is described. The magnetic properties of dense matter are presented and conclusions are given. 37 refs. (A.S.)
Chiral Relaxation Time at the Chiral Crossover of Quantum Chromodynamics
Ruggieri, M; Chernodub, M
2016-01-01
We study microscopic processes responsible for chirality flips in the thermal bath of Quantum Chromodynamics at finite temperature and zero baryon chemical potential. We focus on the temperature range where the crossover from chirally broken phase to quark-gluon plasma takes place, namely $T \\simeq (150, 200)$ MeV. The processes we consider are quark-quark scatterings mediated by collective excitations with the quantum number of pions and $\\sigma$-meson, hence we refer to these processes simply as \\sugg{to} one-pion (one-$\\sigma$) exchange\\sugg{s}. We use a Nambu-Jona-Lasinio model to compute equilibrium properties of the thermal bath, as well as the relevant scattering kernel to be used in the collision integral to estimate the chiral relaxation time $\\tau$. We find $\\tau\\simeq 0.1 \\div 1$ fm/c around the chiral crossover.
ISOSPIN BREAKING AND THE CHIRAL CONDENSATE.
Energy Technology Data Exchange (ETDEWEB)
CREUTZ, M.
2005-07-25
With two degenerate quarks, the chiral condensate exhibits a jump as the quark masses pass through zero. I discuss how this single transition splits into two Ising like transitions when the quarks are made non-degenerate. The order parameter is the expectation of the neutral pion field. The transitions represent long distance coherent phenomena occurring without the Dirac operator having vanishingly small eigenvalues.
Vijande, Javier; Barnea, N.; Richard, J. M.; Valcarce, A.
2009-01-01
The physics of charm has become one of the best laboratories exposing the limitations of the naive constituent quark model and also giving hints into a more mature description of meson spectroscopy, beyond the simple quark--antiquark configurations. In this talk we review some recent studies of multiquark components in the charm sector and discuss in particular exotic and non-exotic four-quark systems, both with pairwise and many-body forces.
Chiral Lagrangian from Duality and Monopole Operators in Compactified QCD
Cherman, Aleksey; Unsal, Mithat
2016-01-01
We show that there exists a special compactification of QCD on $\\mathbb{R}^3 \\times S^1$ in which the theory has a domain where continuous chiral symmetry breaking is analytically calculable. We give a microscopic derivation of the chiral lagrangian, the chiral condensate, and the Gell-Mann-Oakes-Renner relation $m_{\\pi}^2 f_{\\pi}^2 = m_q \\langle \\bar{q} q \\rangle$. Abelian duality, monopole operators, and flavor-twisted boundary conditions, or a background flavor holonomy, play the main roles. The flavor twisting leads to the new effect of fractional jumping of fermion zero modes among monopole-instantons. Chiral symmetry breaking is induced by monopole-instanton operators, and the Nambu-Goldstone pions arise by color-flavor transmutation from gapless "dual photons". We also give a microscopic picture of the "constituent quark" masses. Our results are consistent with expectations from chiral perturbation theory at large $S^1$, and yield strong support for adiabatic continuity between the small-$S^1$ and larg...
Chiral Lagrangian from Duality and Monopole Operators in Compactified QCD
Cherman, Aleksey; Schäfer, Thomas; Ünsal, Mithat
2016-08-01
We show that there exists a special compactification of QCD on R3×S1 in which the theory has a domain where continuous chiral symmetry breaking is analytically calculable. We give a microscopic derivation of the chiral Lagrangian, the chiral condensate, and the Gell-Mann-Oakes-Renner relation mπ2fπ2=-mq⟨q ¯ q ⟩ . Abelian duality, monopole operators, and flavor-twisted boundary conditions play the main roles. The flavor twisting leads to the new effect of fractional jumping of fermion zero modes among monopole instantons. Chiral symmetry breaking is induced by monopole-instanton operators, and the Nambu-Goldstone pions arise by color-flavor transmutation from gapless "dual photons." We also give a microscopic picture of the "constituent quark" masses. Our results are consistent with expectations from chiral perturbation theory at large S1, and yield strong support for adiabatic continuity between the small-S1 and large-S1 regimes. We also find concrete microscopic connections between N =1 and N =2 supersymmetric gauge theory dynamics and nonsupersymmetric QCD dynamics.
Chiral Baryon with Quantized Pions
McNeil, J A
1993-01-01
We study a hybrid chiral model for the nucleon based on the linear sigma model with explicit quarks. We solve the model using a Fock-space configuration consisting of three quarks plus three quarks and a pion as the ground state ansatz in place of the ``hedgehog'' ansatz. We minimize the expectation value of the chiral hamiltonian in this ground state configuration and solve the resulting equations for nucleon quantum numbers. We calculate the canonical set of nucleon observables and compare with previous work.
Inhomogeneous Polyakov loop induced by inhomogeneous chiral condensates
Energy Technology Data Exchange (ETDEWEB)
Hayata, Tomoya, E-mail: hayata@riken.jp [Department of Physics, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Theoretical Research Division, Nishina Center, RIKEN, Wako, Saitama 351-0198 (Japan); Yamamoto, Arata [Department of Physics, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Theoretical Research Division, Nishina Center, RIKEN, Wako, Saitama 351-0198 (Japan)
2015-05-11
We study the spatial inhomogeneity of the Polyakov loop induced by inhomogeneous chiral condensates. We formulate an effective model of gluons on the background fields of chiral condensates, and perform its lattice simulation. On the background of inhomogeneous chiral condensates, the Polyakov loop exhibits an in-phase spatial oscillation with the chiral condensates. We also analyze the heavy quark potential and show that the inhomogeneous Polyakov loop indicates the inhomogeneous confinement of heavy quarks.
Inhomogeneous Polyakov loop induced by inhomogeneous chiral condensates
Directory of Open Access Journals (Sweden)
Tomoya Hayata
2015-05-01
Full Text Available We study the spatial inhomogeneity of the Polyakov loop induced by inhomogeneous chiral condensates. We formulate an effective model of gluons on the background fields of chiral condensates, and perform its lattice simulation. On the background of inhomogeneous chiral condensates, the Polyakov loop exhibits an in-phase spatial oscillation with the chiral condensates. We also analyze the heavy quark potential and show that the inhomogeneous Polyakov loop indicates the inhomogeneous confinement of heavy quarks.
Inhomogeneous Polyakov loop induced by inhomogeneous chiral condensates
Hayata, Tomoya; Yamamoto, Arata
2015-05-01
We study the spatial inhomogeneity of the Polyakov loop induced by inhomogeneous chiral condensates. We formulate an effective model of gluons on the background fields of chiral condensates, and perform its lattice simulation. On the background of inhomogeneous chiral condensates, the Polyakov loop exhibits an in-phase spatial oscillation with the chiral condensates. We also analyze the heavy quark potential and show that the inhomogeneous Polyakov loop indicates the inhomogeneous confinement of heavy quarks.
Chiral gap effect in curved space
Flachi, Antonino
2014-01-01
We discuss a new type of QCD phenomenon induced in curved space. In the QCD vacuum a mass gap of Dirac fermions is attributed to the spontaneous breaking of chiral symmetry. If the curvature is positive large, the chiral condensate melts but a chiral invariant mass gap can still remain, which we name the chiral gap effect in curved space. This leads to decoupling of quark deconfinement which implies a view of black holes surrounded by a first-order QCD phase transition.
SPONTANEOUS CP VIOLATION AND QUARK MASS AMBIGUITIES.
Energy Technology Data Exchange (ETDEWEB)
CREUTZ,M.
2004-09-21
I explore the regions of quark masses where CP will be spontaneously broken in the strong interactions. The boundaries of these regions are controlled by the chiral anomaly, which manifests itself in ambiguities in the definition of non-degenerate quark masses. In particular, the concept of a single massless quark is ill defined.
Lattice QCD thermodynamics with Wilson quarks
Ejiri, Shinji
2007-01-01
We review studies of QCD thermodynamics by lattice QCD simulations with dynamical Wilson quarks. After explaining the basic properties of QCD with Wilson quarks at finite temperature including the phase structure and the scaling properties around the chiral phase transition, we discuss the critical temperature, the equation of state and heavy-quark free energies.
Quark Masses and Renormalization Constants from Quark Propagator and 3-point Functions
Becirevic, D.; Lubicz, V.; Martinelli, G.; Testa, M.(INFN Laboratori Nazionali di Frascati, Frascati, Italy)
1999-01-01
We have computed the light and strange quark masses and the renormalization constants of the quark bilinear operators, by studying the large-p^2 behaviour of the lattice quark propagator and 3-point functions. The calculation is non-perturbatively improved, at O(a), in the chiral limit. The method used to compute the quark masses has never been applied so far, and it does not require an explicit determination of the quark mass renormalization constant.
Baryons in the unquenched quark model
Bijker, R; Lopez-Ruiz, M A; Santopinto, E
2016-01-01
In this contribution, we present the unquenched quark model as an extension of the constituent quark model that includes the effects of sea quarks via a $^{3}P_{0}$ quark-antiquark pair-creation mechanism. Particular attention is paid to the spin and flavor content of the proton, magnetic moments and $\\beta$ decays of octet baryons.
Chiral phase transition in the vector meson extended linear sigma model
Kovács, Péter; Wolf, György
2015-01-01
In the framework of an SU(3) (axial)vector meson extended linear sigma model with additional constituent quarks and Polyakov loops, we investigate the effects of (axial)vector mesons on the chiral phase transition. The parameters of the Lagrangian are set at zero temperature and we use a hybrid approach where in the effective potential the constituent quarks are treated at one-loop level and all the mesons at tree-level. We have four order parameters, two scalar condensates and two Polyakov loop variables and their temperature and baryochemical potential dependence are determined from the corresponding field equations. We also investigate the changes of the tree-level scalar meson masses in the hot and dense medium.
Schwinger functions, light-quark bound states and sigma terms
Höll, A.; Maris, P.; Roberts, C. D.; Wright, S. V.
2006-11-01
We explore the viability of using solely spacelike information about a Schwinger function to extract properties of bound states. In a concrete example it is not possible to determine properties of states with masses ≳1.2 GeV. Modern Dyson-Schwinger equation methods supply a well-constrained tool that provides access to hadron masses and σ-terms. We report values of the latter for a range of hadrons. Of interest is an analysis relating to a u,d scalar meson, which is compatible with a picture of the lightest 0 as a bound state of a dressed-quark and -antiquark supplemented by a material pion cloud. A constituent-quark σ-term is defined, which affords a means for assessing the flavour-dependence of dynamical chiral symmetry breaking.
Instanton-dyon Ensembles III: Exotic Quark Flavors
Larsen, Rasmus
2016-01-01
"Exotic quarks" in the title refers to a modification of quark periodicity condition on the thermal circle by introduction of some phases -- known also as "flavor holonomies" -- different quark flavors. These phases provide a valuable tool, to be used for better understanding of deconfinement and chiral restoration phase transitions: by changing them one can dramatically modify both phase transitions. In the language of instanton constituents -- instanton-dyons or monopoles -- it has a very direct explanation: the interplay of flavor and color holonomies can switch topological zero modes between various dyon types. The model we will study in detail, the so called $Z_{N_c}$-symmetric QCD model with equal number of colors and flavors $N_c=N_f=2$ and special arrangement of flavor and color holonomies, ensure "most democratic" setting, in which each quark flavor and each dyon type are in one-to-one correspondence. The usual QCD has the opposite "most exclusive" arrangement: all quarks are antiperiodic and thus al...
II. The mass gap and solution of the quark confinement problem in QCD
Gogokhia, V.
2007-01-01
We have investigated a closed system of equations for the quark propagator, obtained earlier within our general approach to QCD at low energies. It implies quark confinement (the quark propagator has no pole, indeed), as well as the dynamical breakdown of chiral symmetry (a chiral symmetry preserving solution is forbidded). This system can be solved exactly in the chiral limit. We have established the space of the smooth test functions (consisting of the Green's functions for the quark propag...
A quark structure of hadrons and nuclei
International Nuclear Information System (INIS)
In this review we look into the recent understanding of mesons, baryons and nuclei as few quark bound states within the framework of quantum chromodynamics (QCD). In particular, we have reviewed our understanding of the nature of confining interaction, the spin - dependence of colour forces and the role of non-perturbative effects in the study of quark forces in the potential model approach. We also give a comparative study of results obtained by several potential models with reference to the experimental data. We find that although the Lorentz nature of confinement and the nature of spin-dependent colour forces have been better understood now, only a partial understanding of these problems are obtained so far. Our study reveals that properties of baryons could be explained by the same potential model which successfully describe the mesons. However, the nuclei require chiral symmetry and non-perturbative methods for their description. We also discuss the relation between constituent, current and dynamical quark masses. We conclude that QCD motivated approaches have shown much success in explaining many results on hadronic and nuclear data. (author). 212 refs, 14 tabs
Toy model for two chiral nonets
Fariborz, A H; Schechter, J; Fariborz, Amir H.; Jora, Renata; Schechter, Joseph
2005-01-01
Motivated by the possibility that nonets of scalar mesons might be described as mixtures of "two quark" and "four quark" components, we further study a toy model in which corresponding chiral nonets (containing also the pseudoscalar partners) interact with each other. Although the "two quark" and "four quark" chiral fields transform identically under SU(3)$_L \\times$ SU(3)$_R$ transformations they transform differently under the U(1)$_A$ transformation which essentially counts total (quark + antiquark) content of the mesons. To implement this we formulate an effective Lagrangian which mocks up the U(1)$_A$ behavior of the underlying QCD. We derive generating equations which yield Ward identity type relations based only on the assumed symmetry structure. This is applied to the mass spectrum of the low lying pseudoscalars and scalars. as well as their "excitations". Assuming isotopic spin invariance, it is possible to disentangle the amount of"two quark" vs."four quark" content in the pseudoscalar $\\pi, K ,\\eta...
Personal recollections on chiral symmetry breaking
Kobayashi, Makoto
2016-07-01
The author's work on the mass of pseudoscalar mesons is briefly reviewed. The emergence of the study of CP violation in the renormalizable gauge theory from consideration of chiral symmetry in the quark model is discussed.
International Nuclear Information System (INIS)
After a general introduction to the structure of effective field theories, the main ingredients of chiral perturbation theory are reviewed. Applications include the light quark mass ratios and pion-pion scattering to two-loop accuracy. In the pion-nucleon system, the linear σ model is contrasted with chiral perturbation theory. The heavy-nucleon expansion is used to construct the effective pion-nucleon Lagrangian to third order in the low-energy expansion, with applications to nucleon Compton scattering. (author)
Propagators and Masses of Light Quarks
Institute of Scientific and Technical Information of China (English)
ZHOU Li-Juan; ZHU Ji-Zhen; MA Wei-Xing
2003-01-01
Based on Dyson-Schwinger equations in "rainbow" approximation, fully dressed confining quark propagator is obtained, and then the masses of light quarks (mu, md, and ms) are derived from the fully dressed confining quark propagator. At the same time, the local and non-local quark vacuum condensates as well as the quark-gluon mixed condensate are also predicted. Furthermore, the quark masses are also deduced from the Gell-Mann-Oakes-Renner relation and chiral perturbative theory. The results from different methods are consistent with each other.
Propagators and Masses of Light Quarks
Institute of Scientific and Technical Information of China (English)
ZHOULi-Juan; ZHUJi-Zhen; MAWei-Xing
2003-01-01
Based on Dyson-Schwinger equations in “rainbow” approximation, fully dressed confining quark propagator is obtained, and then the masses of light quarks (mu, md, and ms) are derived from the fully dressed confining quark propagator. At the same time, the local and non-local quark vacuum condensates as well as the quark-gluon mixed condensate are also predicted. Furthermore, the quark masses are also deduced from the Gell-Mann-Oakes-Renner relation and chiral perturbative theory. The results from different methods are consistent with each other.
Neutrino emissivities in 2SC color-superconducting quark matter
Berdermann, J.
2007-01-01
The phase structure and equation of state for two-flavor quark matter under compact star constraints is studied within a nonlocal chiral quark model. Chiral symmetry breaking leads to rather large, density dependent quark masses at the phase transition to quark matter. The influence of diquark pairing gaps and quark masses on density dependent emissivities for the direct URCA is discussed. Since m_u>m_d, the direct URCA process due to quark masses cannot occur. We present cooling curves for m...
Unphysical phases in staggered chiral perturbation theory
Aubin, Christopher; Colletti, Katrina; Davila, George
2016-04-01
We study the phase diagram for staggered quarks using chiral perturbation theory. In beyond-the-standard-model simulations using a large number (>8 ) of staggered fermions, unphysical phases appear for coarse enough lattice spacing. We argue that chiral perturbation theory can be used to interpret one of these phases. In addition, we show that only three broken phases for staggered quarks exist, at least for lattice spacings in the regime a2≪ΛQCD2 .
Partial restoration of chiral symmetry in the color flux tube
Iritani, Takumi; Hashimoto, Shoji
2015-01-01
Using the quark eigenmodes computed on the lattice with the overlap-Dirac operator, we investigate the spatial distribution of the chiral condensate around static color sources corresponding to quark-antiquark and three-quark systems. A flux structure of chromo fields appears in the presence of such color charges. The magnitude of the chiral condensate is reduced inside the color flux, which implies partial restoration of chiral symmetry inside hadrons. Taking a static baryon source in a periodic box as a toy model of the nuclear matter, we estimate the magnitude of the chiral symmetry restoration as a function of baryon matter density.
Chiral thermodynamics of nuclear matter
Energy Technology Data Exchange (ETDEWEB)
Fiorilla, Salvatore
2012-10-23
The equation of state of nuclear matter is calculated at finite temperature in the framework of in-medium chiral perturbation theory up to three-loop order. The dependence of its thermodynamic properties on the isospin-asymmetry is investigated. The chiral quark condensate is evaluated for symmetric nuclear matter. Its behaviour as a function of density and temperature sets important nuclear physics constraints for the QCD phase diagram.
Chiral thermodynamics of nuclear matter
International Nuclear Information System (INIS)
The equation of state of nuclear matter is calculated at finite temperature in the framework of in-medium chiral perturbation theory up to three-loop order. The dependence of its thermodynamic properties on the isospin-asymmetry is investigated. The chiral quark condensate is evaluated for symmetric nuclear matter. Its behaviour as a function of density and temperature sets important nuclear physics constraints for the QCD phase diagram.
Simulations with different lattice Dirac operators for valence and sea quarks
Baer, O.; Rupak, G.; Shoresh, N
2002-01-01
We discuss simulations with different lattice Dirac operators for sea and valence quarks. A goal of such a "mixed" action approach is to probe deeper the chiral regime of QCD by enabling simulations with light valence quarks. This is achieved by using chiral fermions as valence quarks while computationally inexpensive fermions are used in the sea sector. Specifically, we consider Wilson sea quarks and Ginsparg-Wilson valence quarks. The local Symanzik action for this mixed theory is derived t...
Chiral Symmetry Restoration from a Boundary
Tiburzi, B C
2013-01-01
The boundary of a manifold can alter the phase of a theory in the bulk. We explore the possibility of a boundary-induced phase transition for the chiral symmetry of QCD. In particular, we investigate the consequences of imposing homogeneous Dirichlet boundary conditions on the quark fields. Such boundary conditions are employed on occasion in lattice gauge theory computations, for example, when including external electromagnetic fields, or when computing quark propagators with a reduced temporal extent. Homogeneous Dirichlet boundary conditions force the chiral condensate to vanish at the boundary, and thereby obstruct the spontaneous breaking of chiral symmetry in the bulk. As the restoration of chiral symmetry due to a boundary is a non-perturbative phenomenon, we utilize the sigma model to exemplify the issues. Using this model, we find that chiral symmetry is completely restored if the length of the compact direction is less than 2.0 fm. For lengths greater than about 4 fm, an approximately uniform chiral...
Thermal chiral vortical and magnetic waves: new excitation modes in chiral fluids
Kalaydzhyan, Tigran
2016-01-01
In certain circumstances, chiral (parity-violating) medium can be described hydrodynamically as a chiral fluid with microscopic quantum anomalies. Possible examples of such systems include strongly coupled quark-gluon plasma, liquid helium 3He-A, neutron stars and the Early Universe. We study first-order hydrodynamics of a chiral fluid on a vortex background and in a external magnetic field. We show that there are two previously undiscovered modes describing heat waves propagating along the vortex and magnetic field. We call them the Thermal Chiral Vortical Wave and Thermal Chiral Magnetic Wave. We also identify known gapless excitations of density, the chiral vortical and chiral magnetic waves. We demonstrate that the velocity of the chiral vortical wave is zero, when the full hydrodynamic framework is applied, and hence the excitation reduces to a charge diffusion mode or is completely absent. We also correct the dispersion relation for the chiral magnetic wave.
Chiral behavior of light meson form factors in 2+1 flavor QCD with exact chiral symmetry
Kaneko, T; Cossu, G; Feng, X; Fukaya, H; Hashimoto, S; Noaki, J; Onogi, T
2016-01-01
We present a study of chiral behavior of light meson form factors in QCD with three flavors of overlap quarks. Gauge ensembles are generated at single lattice spacing 0.12 fm with pion masses down to 300 MeV. The pion and kaon electromagnetic form factors and the kaon semileptonic form factors are precisely calculated using the all-to-all quark propagator. We discuss their chiral behavior using the next-to-next-to-leading order chiral perturbation theory.
Instanton vacuum at finite density of quark matter
Molodtsov, S. V.; Zinovjev, G. M.
2002-01-01
We study light quark interactions in the instanton liquid at finite quark/baryon number density analyzing chiral and diquark condensates and investigate the behaviors of quark dynamical mass and both condensates together with instanton liquid density as a function of quark chemical potential. We conclude the quark impact (estimated in the tadpole approximation) on the instanton liquid could shift color superconducting phase transition to higher values of the chemical potential bringing critic...
Extended Quark Potential Model From Random Phase Approximation
Institute of Scientific and Technical Information of China (English)
DENGWei－Zhen; CHENXiao－Lin; 等
2002-01-01
The quark potential model is extended to include the sea quark excitation using the random phase approximation.The effective quark interaction preserves the important QCD properties-chiral symmetry and confinement simultaneously.A primary qualitative analysis shows that the π meson as a well-known typical Goldstone boson and the other mesons made up of valence qq quark pair such as the ρ meson can also be described in this extended quark potential model.
Magnetic properties in the inhomogeneous chiral phase
Yoshiike, Ryo; Tatsumi, Toshitaka
2016-01-01
We investigate the magnetic properties of quark matter in the inhomogeneous chiral phase, where both scalar and pseudoscalar condensates spatially modulate. The energy spectrum of the lowest Landau level becomes asymmetric about zero in the external magnetic field, and gives rise to the remarkably magnetic properties: quark matter has a spontaneous magnetization, while the magnetic susceptibility does not diverge on the critical point.
Unexpected manifestation of quark condensation
Energy Technology Data Exchange (ETDEWEB)
Zinovjev, G. M., E-mail: Gennady.Zinovjev@cern.ch [National Academy of Sciences of Ukraine, Bogolyubov Institute for Theoretical Physics (Ukraine); Molodtsov, S. V. [Joint Institute for Nuclear Research (Russian Federation)
2015-05-15
A comparative analysis of some quark ensembles governed by a four-fermion interaction is performed. Arguments in support of the statement that the presence of a gas-liquid phase transition is a feature peculiar to them are adduced. The instability of small quark droplets is discussed and is attributed to the formation of a chiral soliton. The stability of baryon matter is due to a mixed phase of the vacuum and baryon matter.
Chiral restoration at finite T under the magnetic field with the meson-loop corrections
Nam, Seung-il
2011-01-01
We investigate the (partial) chiral restoration at finite temperature (T) under the strong external magnetic field B_0 of the SU(2) light-flavor QCD matter. To this end, we employ the instanton-liquid QCD vacuum configuration accompanied with the linear Schwinger method for inducing the magnetic field. The Harrington-Shepard caloron solution is used to modify the instanton parameters, i.e. the average instanton size (rho) and inter-instanton distance (R), as functions of T. In addition, we include the meson-loop corrections (MLC) as the large-N_c corrections because they are critical for reproducing the universal chiral restoration pattern. We present the numerical results for the constituent-quark mass as well as chiral condensate which signal the spontaneous breakdown of chiral-symmetry SBCS, as functions of T and B_0. From our results we observe that the strengths of those chiral order parameters are enhanced with respect to B_0 due to the magnetic catalysis effect. We also find that there appears a region...
Pallante, E.; R. Petronzio(INFN RM2)
1994-01-01
We construct an effective Lagrangian for low energy hadronic interactions through an infinite expansion in inverse powers of the low energy cutoff Î›Ï‡ of all possible chiral invariant non-renormalizable interactions between quarks and mesons degrees of freedom arising from the bosonization of a general Nambu-Jona Lasinio type Lagrangian including all multiquark effective interactions. We restrict our analysis to the leading terms in the 1/Nc expansion and to the divergent part of the resonan...
Chiral dynamics of heavy-light mesons
International Nuclear Information System (INIS)
This thesis focuses on the physics of heavy-light mesons, i.e. quark-antiquark systems composed of a heavy (c or b) and a light (u, d or s) quark. The light-quark sector is treated within the framework of chiral effective field theory. Recent lattice QCD computations have progressed in determining the decay constants of charmed mesons and the scattering lengths of Nambu-Goldstone bosons (pions, kaons) off D mesons. These computations are performed for light quark masses larger than the physical ones. A chiral extrapolation down to physical masses is necessary. It is commonly performed using chiral perturbation theory. The related systematical uncertainties have to be examined carefully. In this thesis it is shown how these uncertainties can be reduced significantly by taking into account relativistic effects in the chiral extrapolations. As a byproduct, estimates are presented for several physical quantities that are related by heavy-quark spin and flavor symmetry. Furthermore, the investigation of the light-quark mass dependence of the scattering lengths of Nambu-Goldstone bosons off D mesons provides important information on the nature of one of the intriguing newly discovered resonances, the D*s0(2317). It is shown that this resonance can be dynamically generated from the coupled-channels DK interaction without a priori assumption of its existence. Finally we demonstrate how the underlying framework, unitarized chiral perturbation theory, can be improved by the inclusion of intermediate states with off-the-mass-shell kinematics.
Chiral symmetry in perturbative QCD
International Nuclear Information System (INIS)
The chiral symmetry of quantum chromodynamics with massless quarks is unbroken in perturbation theory. Dimensional regularization is used. The ratio of the vector and axial vector renormalization constante is shown to be independent of the renormalization mass. The general results are explicitly verified to fourth order in g, the QCD coupling constant
Instantons and chiral symmetry breaking
International Nuclear Information System (INIS)
A detailed investigation of chiral symmetry breaking due to instanton dynamics is carried out, within the framework of the dilute gas approximation, for quarks in both the fundamental and adjoint representations of SU(2). The momentum dependence of the dynamical mass is found to be very similar in each representation. (orig.)
Inhomogeneous Polyakov loop induced by inhomogeneous chiral condensates
Tomoya Hayata; Arata Yamamoto
2015-01-01
We study the spatial inhomogeneity of the Polyakov loop induced by inhomogeneous chiral condensates. We formulate an effective model of gluons on the background fields of chiral condensates, and perform its lattice simulation. On the background of inhomogeneous chiral condensates, the Polyakov loop exhibits an in-phase spatial oscillation with the chiral condensates. We also analyze the heavy quark potential and show that the inhomogeneous Polyakov loop indicates the inhomogeneous confinement...
Novel Lifshitz point for chiral transition in the magnetic field
Directory of Open Access Journals (Sweden)
Toshitaka Tatsumi
2015-04-01
Full Text Available Based on the generalized Ginzburg–Landau theory, chiral phase transition is discussed in the presence of magnetic field. Considering the chiral density wave we show that chiral anomaly gives rise to an inhomogeneous chiral phase for nonzero quark-number chemical potential. Novel Lifshitz point appears on the vanishing chemical potential line, which may be directly explored by the lattice QCD simulation.
Magnetic test of chiral dynamics in QCD
International Nuclear Information System (INIS)
Strong magnetic fields in the range eB≫mπ2 effectively probe internal quark structure of chiral mesons and test basic parameters of the chiral theory, such as 〈q-barq〉,fπ. We argue on general grounds that 〈q-barq〉 should grow linearly with eB when charged quark degrees of freedom come into play. To make explicit estimates we extend the previously formulated chiral theory, including quark degrees of freedom, to the case of strong magnetic fields and show that the quark condensate |〈q-barq〉|u,d grows quadratically with eB for eB<0.2 GeV2 and linearly for higher field values. These results agree quantitatively with recent lattice data and differ from χPT predictions
SU(2) higher-order effective quark interactions from polarization
Braghin, Fábio L
2016-01-01
Higher order quark effective interactions are found for SU(2) flavor by departing from a non local quark-quark interaction. By integrating out a component of the quark field, the determinant is expanded in chirally symmetric and symmetry breaking effective interactions up to the fifh order in the quark bilinears. The resulting coupling constants are resolved in the leading order of the longwavelength limit and exact numerical ratios between several of these coupling constants are obtained in the large quark mass limit. In this level, chiral invariant interactions only show up in even powers of the quark bilinears, i.e. ${\\cal O}(\\bpsi \\psi)^{2 n}$ ($n=1,2,3,..$), and chiral symmetry breaking terms emerge as ${\\cal O}(\\bpsi \\psi)^{n}$.
Quark Spin and Orbital Angular Momentum in the Baryon
Song, X.
1999-01-01
The spin and orbital angular momentum carried by different quark flavors in the nucleon are calculated in the SU(3) chiral quark model with symmetry-breaking. The model is extended to all octet and decuplet baryons. In this model, the reduction of the quark spin, due to the spin dilution in the chiral splitting processes, is transferred into the orbital motion of quarks and antiquarks. The orbital angular momentum for each quark flavor in the proton as function of the partition factor $\\kappa...
Fok, R
2011-01-01
We calculate the two-body decay rates of "quirkonium" states formed from quirks that acquire mass solely through electroweak symmetry breaking. We consider SU(N)_ic infracolor with two flavors of quirks transforming under the electroweak group (but not QCD) of the Standard Model. In one case, the quirks are in a chiral representation of the electroweak group, while in the other case, a vector-like representation. The differences in the dominant decay channels between "chiral quirkonia" versus "vector-like quirkonia" are striking. Several chiral quirkonia states can decay into the unique two-body resonance channels WH, ZH, t\\bar{t}, t\\bar{b} / b\\bar{t}, and gamma+H, which never dominate for vector-like quirkonia. Additionally, the channels WW, WZ, ZZ, and W+gamma, are shared among both chiral and vector-like quirkonia. Resonances of dileptons or light quarks (dijets) can dominate for some vector-like quirkonia states throughout their mass range, while these modes never dominate for chiral quirkonia unless the ...
International Nuclear Information System (INIS)
We calculate the two-body decay rates of quirkonium states formed from quirks that acquire mass solely through electroweak symmetry breaking. We consider SU(N)ic infracolor with two flavors of quirks transforming under the electroweak group (but not QCD) of the standard model. In one case, the quirks are in a chiral representation of the electroweak group, while in the other case, a vectorlike representation. The differences in the dominant decay channels between 'chiral quirkonia' versus 'vectorlike quirkonia' are striking. Several chiral quirkonia states can decay into the unique two-body resonance channels WH, ZH, tt, tb/bt, and γH, which never dominate for vectorlike quirkonia. Additionally, the channels WW, WZ, ZZ, and Wγ, are shared among both chiral and vectorlike quirkonia. Resonances of dileptons or light quarks (dijets) can dominate for some vectorlike quirkonia states throughout their mass range, while these modes never dominate for chiral quirkonia unless the decays into pairs of gauge or Higgs bosons are kinematically forbidden.
Light-quark, heavy-quark systems: An update
International Nuclear Information System (INIS)
The author reviews many of the recently developed applications of Heavy Quark Effective Theory techniques. After a brief update on Luke's theorm, he describes striking relations between heavy baryon form factors, and how to use them to estimate the accuracy of the extraction of |Bcb|. He discusses factorization and compares with experiment. An elementary presentation, with sample applications, of reparametrization invariance comes next. The final and most extensive chapter in this review deals with phenomenological lagrangians that incorporate heavy-quark spin-flavor as well as light quark chiral symmetries. He compiles many interesting results and discuss the validity of the calculations
Quark Matter in a Strong Magnetic Background
Gatto, Raoul
2012-01-01
In this chapter, we discuss several aspects of the theory of strong interactions in presence of a strong magnetic background. In particular, we summarize our results on the effect of the magnetic background on chiral symmetry restoration and deconfinement at finite temperature. Moreover, we compute the magnetic susceptibility of the chiral condensate and the quark polarization at zero temperature. Our theoretical framework is given by chiral models: the Nambu-Jona-Lasinio (NJL), the Polyakov improved NJL (or PNJL) and the Quark-Meson (QM) models. We also compare our results with the ones obtained by other groups.
Baryon masses with improved staggered quarks
Bernard, C; DeTar, C; Gottlieb, S; Heller, U M; Hetrick, J E; Levkova, L; Osborn, J; Renner, D B; Sugar, R; Toussaint, D
2007-01-01
The MILC collaboration's simulations with improved staggered quarks are being extended with runs at a lattice spacing of 0.06 fm with quark masses down to one tenth the strange quark mass. We give a brief introduction to these new simulations and the determination of the lattice spacing. Then we combine these new runs with older results to study the masses of the nucleon and the Omega minus in the continuum and chiral limits.
Ledwig, Tim; Goeke, Klaus
2008-01-01
We investigate the vector transition form factors of the nucleon and vector meson $K^*$ to the pentaquark baryon $\\Theta^+$ within the framework of the SU(3) chiral quark-soliton model. We take into account the rotational $1/N_c$ and linear $m_{\\rm s}$ corrections, assuming isospin symmetry and employing the symmetry-conserving quantization. It turns out that the leading-order contributions to the form factors are almost cancelled by the rotational corrections. Because of this, the flavor SU(3) symmetry-breaking terms yield sizeable effects on the transition form factors. In particular, the main contribution to the electric transition form factor comes from the wave-function corrections, which is a consequence of the generalized Ademollo-Gatto theorem derived in the present work. We estimate with the help of the vector meson dominance the $K^*$ vector and tensor coupling constants for the $\\Theta^+$: $g_{K^{*}N\\Theta}=0.74 - 0.87$ and $f_{K^{*}N\\Theta}=0.53 - 1.16$. We argue that the outcome of the present wo...
Implications of Local Chiral Symmetry Breaking
La, H S
2003-01-01
The spontaneous symmetry breaking of a local chiral symmetry to its diagonal vector symmetry naturally realizes a complete geometrical structure more general than that of Yang-Mills (YM) theory, rather similar to that of gravity. A good example is the Quantum Chromodynamics (QCD) with respect to the Chiral Color model. Also, a new anomaly-free particle content for a Chiral Color model is introduced: the Chiral Color can be realized without introducing whole new generations of quarks and leptons, but by simply enlarging each generation with new exotic fermions.
Wigner distributions and quark orbital angular momentum
Cedric LorceOrsay, IPN and Orsay, LPT; Barbara Pasquini(Pavia U. and INFN, Pavia)
2015-01-01
We discuss the quark phase-space or Wigner distributions of the nucleon which combine in a single picture all the information contained in the generalized parton distributions and the transverse-momentum dependent parton distributions. In particular, we present results for the distribution of unpolarized quarks in a longitudinally polarized nucleon obtained in a light-front constituent quark model. We show how the quark orbital angular momentum can be extracted from the Wigner distributions a...
Toy model for two chiral nonets
International Nuclear Information System (INIS)
Motivated by the possibility that nonets of scalar mesons might be described as mixtures of 'two quark' and 'four quark' components, we further study a toy model in which corresponding chiral nonets (containing also the pseudoscalar partners) interact with each other. Although the 'two quark' and 'four quark' chiral fields transform identically under SU(3)LxSU(3)R transformations, they transform differently under the U(1)A transformation which essentially counts total (quark+antiquark) content of the mesons. To implement this, we formulate an effective Lagrangian which mocks up the U(1)A behavior of the underlying QCD. We derive generating equations which yield Ward identity type relations based only on the assumed symmetry structure. This is applied to the mass spectrum of the low lying pseudoscalars and scalars, as well as their 'excitations'. Assuming isotopic spin invariance, it is possible to disentangle the amount of 'two quark' vs 'four quark' content in the pseudoscalar π,K,η-type states and in the scalar κ-type states. It is found that a small 'four quark' content in the lightest pseudoscalars is consistent with a large 'four quark' content in the lightest of the scalar κ mesons. The present toy model also allows one to easily estimate the strength of a 'four quark' vacuum condensate. There seems to be a rich and interesting structure
Chiral symmetry breaking and vacuum polarization in a bag
Yasui, S
2006-01-01
We study the effects of a finite quark mass in the hedgehog configuration in the two phase chiral bag model. We discuss the chiral properties, such as the fractional baryon number and the chiral Casimir energy, by using the Debye expansion for the analytical calculation and the Strutinsky's smearing method for the numerical computation. It is shown that the fractional baryon number carried by massive quarks in the vacuum is canceled by that in the meson sector. A finite term of the chiral Casimir energy is obtained with subtraction of the logarithmic divergence term.
Schwinger functions and light-quark bound states, and sigma terms
Höll, A; Roberts, C D; Wright, S V
2006-01-01
We explore the viability of using solely spacelike information about a Schwinger function to extract properties of bound states. In a concrete example it is not possible to determine properties of states with masses \\gsim 1.2 GeV. Modern Dyson-Schwinger equation methods supply a well-constrained tool that provide access to hadron masses and \\sigma-terms. We report values of the latter for a range of hadrons. Of interest is analysis relating to a u,d scalar meson, which is compatible with a picture of the lightest 0^{++} as a bound state of a dressed-quark and -antiquark supplemented by a material pion cloud. A constituent-quark \\sigma-term is defined, which affords a means for assessing the flavour-dependence of dynamical chiral symmetry breaking.
The quark revolution and the ZGS - new quarks physics since the ZGS
International Nuclear Information System (INIS)
Overwhelming experimental evidence for quarks as real physical constituents of hadrons along with the QCD analogs of the Balmer Formula, Bohr Atom and Schroedinger Equation already existed in 1966 but was dismissed as heresy. ZGS experiments played an important role in the quark revolution. This role is briefly reviewed and subsequent progress in quark physics is described
The quark revolution and the ZGS - new quarks physics since the ZGS
Energy Technology Data Exchange (ETDEWEB)
Lipkin, H.J. [Weizmann Institute of Science, Rehovot (Israel)]|[Tel Aviv Univ. (Israel)
1994-12-31
Overwhelming experimental evidence for quarks as real physical constituents of hadrons along with the QCD analogs of the Balmer Formula, Bohr Atom and Schroedinger Equation already existed in 1966 but was dismissed as heresy. ZGS experiments played an important role in the quark revolution. This role is briefly reviewed and subsequent progress in quark physics is described.
Institute of Scientific and Technical Information of China (English)
ZONGHong－Shi; PINGJia－Lun; 等
2002-01-01
We exhibit a method for obtaining the low chemical potential dependence of the dressed quark propagator from the dressed-quark propagator,which provides a means of determining the behavior of the chiral and deconfinement order parameters.A comparison with the results of previous researches is given.
Ward identities and the analogous Goldberger-Treiman relation in a three-flavor Spectral Quark Model
Reis, E. A.; Mota, A. L.; Dias, E. W.
2016-04-01
This work presents the first results of an extension of the spectral quark model which includes different flavors. The spectral quark model is an approach based on a generalization of the Lehmann representation for the quark propagator. Gauge and chiral invariance are ensured with the help of gauge technique which provides particular solutions to the Ward-Takahashi identities. General conditions on the quark spectral function follow from natural physical requirements. In particular, the function is normalized, its positive momenta must vanish, while the physical observables depend on negative moments and the so-called log moments. As a consequence, the model is made finite. To allow the description of mesons constituted by different flavors of quarks we introduce different spectral functions and obtain vertex functions constructed from Ward-Takahashi identities that includes two different spectral (constituent) quark masses, allowing the physical description of strange mesons, for example. We obtain some observables based on the current approach and, in particular, the spectral version of the Kaon analogous Goldberger-Treiman relation.
Extended Quark Potential Model from Random Phase Approximation
Institute of Scientific and Technical Information of China (English)
DENG Wei-Zhen; CHEN Xiao-Lin; LU Da-Hai; YANG Li-Ming
2002-01-01
The quark potential model is extended to include the sea quark excitation using the random phase approx-imation. The effective quark interaction preserves the important QCD properties - chiral symmetry and confinementsimultaneously. A primary qualitative analysis shows that the π meson as a well-known typical Goldstone boson andthe other mesons made up of valence qq quark pair such as the ρ meson can also be described in this extended quarkpotential model.
Flavor Asymmetry of the Sea Quarks in the Baryon Octet
Koretune, Susumu
1998-01-01
We show that the chiral $SU(n)\\otimes SU(n)$ flavor symmetry on the null-plane severely restricts the sea quarks in the baryon octet. It predicts large asymmetry for the light sea quarks $(u,d,s)$, and universality and abundance for the heavy sea quarks. Further it is shown that existence of the heavy sea quarks constrained by the same symmetry reduces the theoretical value of the Ellis-Jaffe sum rule substantially.
Chiral perturbation theory with nucleons
International Nuclear Information System (INIS)
I review the constraints posed on the interactions of pions, nucleons and photons by the spontaneously broken chiral symmetry of QCD. The framework to perform these calculations, chiral perturbation theory, is briefly discussed in the meson sector. The method is a simultaneous expansion of the Greens functions in powers of external moments and quark masses around the massless case, the chiral limit. To perform this expansion, use is made of a phenomenological Lagrangian which encodes the Ward-identities and pertinent symmetries of QCD. The concept of chiral power counting is introduced. The main part of the lectures of consists in describing how to include baryons (nucleons) and how the chiral structure is modified by the fact that the nucleon mass in the chiral limit does not vanish. Particular emphasis is put on working out applications to show the strengths and limitations of the methods. Some processes which are discussed are threshold photopion production, low-energy compton scattering off nucleons, πN scattering and the σ-term. The implications of the broken chiral symmetry on the nuclear forces are briefly described. An alternative approach, in which the baryons are treated as very heavy fields, is touched upon
Kojo, Toru; Fukushima, Kenji; McLerran, Larry; Pisarski, Robert D
2011-01-01
We elaborate how to construct the interweaving chiral spirals in (2+1) dimensions, that is defined as a superposition of differently oriented chiral spirals. We divide the two-dimensional Fermi sea into distinct wedges characterized by the opening angle 2 Theta and the depth Q \\simeq pF, where pF is the Fermi momentum. Each wedge earns an energy gain by forming a single chiral spiral. The optimal values for Theta and Q are chosen by the balance between this energy gain and the energy costs from the deformed Fermi surface (dominant at large Theta) and patch-patch interactions (dominant at small Theta). We estimate these energy gains and costs by means of the expansions in terms of 1/Nc, Lambda_QCD/Q, and Theta using a non-local four-Fermi interaction model: At small 1/Nc the mass gap (chiral condensate) is large enough and the interaction among quarks and the condensate is local in momentum space thanks to the form factor in our non-local model. The fact that patch-patch interactions lie only near the patch bo...
Rho, Mannque
2008-01-01
This is the sequel to the first volume to treat in one effective field theory framework the physics of strongly interacting matter under extreme conditions. This is vital for understanding the high temperature phenomena taking place in relativistic heavy ion collisions and in the early Universe, as well as the high-density matter predicted to be present in compact stars. The underlying thesis is that what governs hadronic properties in a heat bath and/or a dense medium is hidden local symmetry which emerges from chiral dynamics of light quark systems and from the duality between QCD in 4D and
The vector manifestation and effective degrees of freedom at chiral restoration
International Nuclear Information System (INIS)
The role of effective degrees of freedom on the vector and axial-vector susceptibilities and the pion velocity at chiral restoration is analyzed. We consider two possible scenarios, one in which pions are considered to be the only low-lying degrees of freedom - that we shall refer to as 'standard' - and the other in which pions, vector mesons and constituent quarks (or quasiquarks in short) are the relevant low-lying degrees of freedom - that we shall refer to as 'vector manifestation (VM)'. We show at one-loop order in chiral perturbation theory with hidden local symmetry Lagrangian that while in the standard scenario, the pion velocity vanishes at the chiral transition, it instead approaches unity in the VM scenario. If the VM is realized in nature, the chiral phase structure of hadronic matter can be much richer than that in the standard one and the phase transition will be a smooth crossover: Sharp vector and scalar excitations are expected in the vicinity of the critical point. Some indirect indications that lend support to the VM scenario, and in consequence to BR scaling, are discussed. (author)
Analysis of chiral symmetry breaking mechanism
International Nuclear Information System (INIS)
The renormalization group invariant quark condensate μ is determinate both from the consistent equation for quark condensate in the chiral limit and from the Schwinger-Dyson (SD) equation improved by the intermediate range QCD force singular like δ (q) which is associated with the gluon condensate. The solutions of μ in these two equations are consistent. We also obtain the critical strong coupling constant αc above which chiral symmetry breaks in two approaches. The nonperturbative kernel of the SD equation makes αc smaller and μ bigger. An intuitive picture of the condensation above αc is discussed. In addition, with the help of the Slavnov-Taylor-Ward (STW) identity we derive the equations for the nonperturbative quark propagator from SD equation in the presence of the intermediate-range force is also responsible for dynamical chiral symmetry breaking. (author)
Hyperfine meson splittings: chiral symmetry versus transverse gluon exchange
Llanes-Estrada, Felipe J; Swanson, Eric S; Szczepaniak, Adam P; Llanes-Estrada, Felipe J.; Cotanch, Stephen R.; Szczepaniak, Adam P.; Swanson, Eric S.
2004-01-01
Meson spin splittings are examined within an effective Coulomb gauge QCD Hamiltonian incorporating chiral symmetry and a transverse hyperfine interaction necessary for heavy quarks. For light and heavy quarkonium systems the pseudoscalar-vector meson spectrum is generated by approximate BCS-RPA diagonalizations. This relativistic formulation includes both $S$ and $D$ waves for the vector mesons which generates a set of coupled integral equations. A smooth transition from the heavy to the light quark regime is found with chiral symmetry dominating the $\\pi$-$\\rho$ mass difference. A good, consistent description of the observed meson spin splittings and chiral quantities, such as the quark condensate and the $\\pi$ mass, is obtained. Similar comparisons with TDA diagonalizations, which violate chiral symmetry, are deficient for light pseudoscalar mesons indicating the need to simultaneously include both chiral symmetry and a hyperfine interaction. The $\\eta_b$ mass is predicted to be around 9400 MeV consistent w...
Transversity of quarks in a nucleon
Indian Academy of Sciences (India)
K Bora; D K Choudhury
2003-11-01
The transversity distribution of quarks in a nucleon is one of the three fundamental distributions, that characterize nucleon’s properties in hard scattering processes at leading twist (twist 2). It measures the distribution of quark transverse spin in a nucleon polarized transverse to its (inﬁnite) momentum. It is a chiral-odd twist-two distribution function – gluons do not couple to it. Quarks in a nucleon/hadron are relativistically bound and transversity is a measure of the relativistic nature of bound quarks in a nucleon. In this work, we review some important aspects of this less familiar distribution function which has not been measured experimentally so far.
Quarks and gluons in a magnetic field
Watson, Peter
2013-01-01
The quark gap equation under the rainbow truncation, with two versions of a phenomenological one-gluon exchange interaction and in the presence of a uniform magnetic field is considered. It is argued that in order to describe the quark condensate in the limit of vanishing magnetic fields, one must sum over the Landau levels. The resulting chiral quark condensate rises quadratically for small magnetic fields and linearly for large fields, in qualitative agreement with various recent lattice results. It is observed that when discussing quarks, the magnitude of the magnetic field must be considered relative to the scale of the strong interaction.
Staggered Heavy Baryon Chiral Perturbation Theory
Bailey, Jon A
2007-01-01
Although taste violations significantly affect the results of staggered calculations of pseudoscalar and heavy-light mesonic quantities, those entering staggered calculations of baryonic quantities have not been quantified. Here I develop staggered chiral perturbation theory in the light-quark baryon sector by mapping the Symanzik action into heavy baryon chiral perturbation theory. For 2+1 dynamical quark flavors, the masses of flavor-symmetric nucleons are calculated to third order in partially quenched and fully dynamical staggered chiral perturbation theory. To this order the expansion includes the leading chiral logarithms, which come from loops with virtual decuplet-like states, as well as terms the order of the cubed pion mass, which come from loops with virtual octet-like states. Taste violations enter through the meson propagators in loops and tree-level terms the order of the squared lattice spacing. The pattern of taste symmetry breaking and the resulting degeneracies and mixings are discussed in d...
Inoue, Yoshihisa
2004-01-01
Direct Asymmetric Photochemistry with Circularly Polarized Light, H. RauCoherent Laser Control of the Handedness of Chiral Molecules, P. Brumer and M. ShapiroMagnetochiral Anisotropy in Asymmetric Photochemistry, G.L.J.A.RikkenEnantiodifferentiating Photosensitized Reactions, Y. InoueDiastereodifferentiating Photoreactions, N. Hoffmann and J.-P. PeteChirality in Photochromism, Y. Yokoyama and M. SaitoChiral Photochemistry with Transition Metal Complexes, S. Sakaki and T. HamadaTemplate-Induced Enantioselective Photochemical Reactions in S
Kharzeev, Dmitri E.; Yee, Ho-Ung
2012-01-01
We consider the properties of electric circuits involving Weyl semimetals. The existence of the anomaly-induced chiral magnetic current in a Weyl semimetal subjected to magnetic field causes an interesting and unusual behavior of such circuits. We consider two explicit examples: i) a circuit involving the "chiral battery" and ii) a circuit that can be used as a "quantum amplifier" of magnetic field. The unique properties of these circuits stem from the chiral anomaly and may be utilized for c...
Field induced spin chirality and chirality switching in magnetic multilayers
International Nuclear Information System (INIS)
The physical origin of the field-induced spin chirality experimentally observed in rare earth multilayers is determined. It is shown that the effect is possible due to the interplay between solid-state exchange interactions (the Ruderman–Kittel–Kasuya–Yosida and the Dsyaloshinsky–Moriya interactions), the external magnetic field and a special confinement of magnetic constituents. The presented model describes a certain temperature dependence of the chirality factor in agreement with experimental data and opens a new way to design nanostructured objects with predicted handedness. - Highlights: • Field-induced spin chirality in magnetic multilayers is explained. • The roles of the RKKY, the DM and the Zeeman interactions are clarified. • Theoretical analysis of the chirality factor is in agreement with experimental data
Chiral effective model with the Polyakov loop
Fukushima, Kenji
2003-01-01
We discuss how the simultaneous crossovers of deconfinement and chiral restoration can be realized. We propose a dynamical mechanism assuming that the effective potential gives a finite value of the chiral condensate if the Polyakov loop vanishes. Using a simple model, we demonstrate that our idea works well for small quark mass, though there should be further constraints to reach the perfect locking of two phenomena.
Chiral symmetry and lattice gauge theory
International Nuclear Information System (INIS)
I review the problem of formulating chiral symmetry in lattice gauge theory. I discuss recent approaches involving an infinite tower of additional heavy states to absorb Fermion doublers. For hadronic physics this provides a natural scheme for taking quark masses to zero without requiring a precise tuning of parameters. A mirror Fermion variation provides a possible way of extending the picture to chirally coupled light Fermions
Neutral B Mixing in Staggered Chiral Perturbation Theory
Bernard, C
2013-01-01
I calculate, at one loop in staggered chiral perturbation theory, the matrix elements of the complete set of five local operators that may contribute to B mixing both in the Standard Model and in beyond-the-Standard-Model theories. Lattice computations of these matrix elements by the Fermilab Lattice/MILC collaborations (and earlier by the HPQCD collaboration) convert a light staggered quark into a naive quark, and construct the relevant 4-quark operators as local products of two local bilinears, each involving the naive light quark and the heavy quark. This particular representation of the operators turns out to be important in the chiral calculation, and it results in the presence of "wrong-spin" operators, whose contributions however vanish in the continuum limit. If the matrix elements of all five operators are computed on the lattice, then no additional low energy constants are required to describe wrong-spin chiral effects.
Relating lattice QCD and chiral perturbation theory
International Nuclear Information System (INIS)
We present simulation results for lattice QCD using chiral lattice fermions, which obey the Ginsparg Wilson relation. After discuss first conceptual issues, and then numerical results. In the epsilon regime we evaluated the low lying modes in Dirac spectrum and the axial correlation functions for very light quarks. These provide information about the leading low energy constants in chiral perturbation theory: the pion decay constant and the scalar condensate. In the p regime we measured light meson masses, the PCAC quark mass and the renormalisation constant ZA
QCD thermodynamics with colour-sextet quarks
Sinclair, D K
2009-01-01
We study QCD with two flavours of colour-sextet quarks as a candidate walking-Technicolor theory. We simulate lattice QCD with two flavours of colour-sextet staggered quarks at finite temperatures to observe the scales of confinement and chiral-symmetry breaking. These should give us some indication as to whether the massless theory has an infrared fixed point making it a conformal field theory, or whether it exhibits confinement and chiral symmetry breaking with a slowly varying coupling constant, i.e. `walks'. We find that unlike the case with fundamental quarks, the deconfinement and chiral-symmetry restoration transitions are far apart. The values of $\\beta=6/g^2$ for both transitions increase when $Ta$ is decreased from 1/4 to 1/6 as would be expected for finite temperature transitions of an asymptotically-free field theory. So far we see no suggestion of conformal behaviour.
Top quark mass measurements in ATLAS
International Nuclear Information System (INIS)
The top quark is a fundamental constituent of the Standard Model (SM). The properties of this quark are accurately predicted by this theory, except for its mass, which remains a fundamental parameter of the SM. With the advent of the Large Hadron Collider (LHC), many million of top-antitop quark pairs are available for study. With such statistics, the physics of the top quark has entered the precision era. In this note, the most recent experimental results by ATLAS concerning the top quark mass are reported
Smith, F T
1997-01-01
From sets and simple operations on sets, a Feynman Checkerboard physics model is constructed that allows computation of force strength constants and constituent mass ratios of elementary particles, giving a tree level constituent Truth Quark (top quark) mass of roughly 130 GeV, which is (in my opinion) supported by dileptonic events and some semileptonic events. See http://galaxy.cau.edu/tsmith/HDFCmodel.html and http://www.innerx.net/personal/tsmith/HDFCmodel.html This model is similar to a Lie algebra D4-D5-E6 model: Chapter 1 - Introduction. Chapter 2 - From Sets to Clifford Algebras. Chapter 3 - Octonions and E8 lattices. Chapter 4 - E8 spacetime and particles. Chapter 5 - HyperDiamond Lattices. Chapter 6 - Internal Symmetry Space. Chapter 7 - Feynman Checkerboards. Chapter 8 - Charge = Amplitude to Emit Gauge Boson. Chapter 9 - Mass = Amplitude to Change Direction. Chapter 10 - Protons, Pions, and Physical Gravitons.
On the overlap formulation of chiral gauge theory
International Nuclear Information System (INIS)
The overlap formula proposed by Narayanan and Neuberger in chiral gauge theories is examined. The free chiral and Dirac Green's functions are constructed in this formalism. Four dimensional anomalies are calculated and the usual anomaly cancellation for one standard family of quarks and leptons is verified. (author). 4 refs
Chiral symmetry in hadron physics methods and ideas of chiral symmetry
International Nuclear Information System (INIS)
Methods and ideas of chiral symmetry is presented based on a lecture note to help the future researches in hadron dynamics along with the chiral symmetry. The chiral symmetry was originally developed as the symmetry between currents before the discovery of QCD. It has come to be understood in principle by now that the symmetry is spontaneously broken and only the part of flavor symmetry remains explicitly. In QCD, however, the chiral symmetry has come to be regarded as the base of the symmetry of the global flavor space of quarks. One of the recent topics of the lattice gauge theory is how the hadron properties will change when the broken symmetry is going to be restored. Since the chiral symmetry is global, it is different from gauge symmetry which is local. It explains the degeneracy of hadron masses and relations between the elements of S-matrix in which same number of particles are included. In practice, however, the symmetry of the axial part is spontaneously broken and pions which behave like gauge particles come to play. Chiral symmetry is defined as the (internal) flavor symmetry for the two independent chirality states of quarks. It discriminates two different fundamental quarks defined for the Lorentz groups O(4) - SL(2, C). The symmetry transformation itself is, however, different from the chirality. They should not be confused. In this lecture note, fundamental properties of pions are described on the basis of the interaction with nucleons at first. General properties of the chiral symmetry and some of the low energy theorems on current algebra are introduced. Then, linear sigma model and nonlinear sigma model are introduced. Then the Skyrme-model, which provides an idea as important as quarks, is explained. One of the interesting topics at present is to restore the broken axial symmetry experimentally to investigate the mechanism of symmetry breaking. (S. Funahashi)
Chiral dynamics and operator relations at non-zero chemical potential
International Nuclear Information System (INIS)
We discuss Taylor expansions of operator expectation values in QCD with respect to chemical potentials of quarks. Maxwell's relations between coefficients and Ward identities between series are used to relate the operators which give the Taylor coefficients of the series for the chiral condensate, the pseudoscalar susceptibility and the mass dependence of quark number susceptibilities. Through such relations the physics of chiral dynamics are explored. The renormalized expectation values of the chiral condensate and its Taylor coefficients are extracted from simulation
Dynamical quark mass generation in a strong external magnetic field
International Nuclear Information System (INIS)
We investigate the effect of a strong magnetic field on dynamical chiral symmetry breaking in quenched and unquenched QCD. To this end we apply the Ritus formalism to the coupled set of (truncated) Dyson-Schwinger equations for the quark and gluon propagator under the presence of an external constant Abelian magnetic field. We discuss the effect of the magnetic field onto the quark condensate and extract the chiral susceptibility.
Energy Technology Data Exchange (ETDEWEB)
Gupta, R.
1994-12-31
This talk contains an analysis of quenched chiral perturbation theory and its consequences. The chiral behavior of a number of quantities such as the pion mass m{sub pi}{sup 2}, the Bernard-Golterman ratios R and {sub X}, the masses of nucleons, and the kaon B-parameter are examined to see if the singular terms induced by the additional Goldstone boson, {eta}{prime}, are visible in present data. The overall conclusion (different from that presented at the lattice meeting) of this analysis is that even though there are some caveats attached to the indications of the extra terms induced by {eta}{prime} loops, the standard expressions break down when extrapolating the quenched data with m{sub q} < m{sub s}/2 to physical light quarks. I then show that due to the single and double poles in the quenched {eta}{prime}, the axial charge of the proton cannot be calculated using the Adler-Bell-Jackiw anomaly condition. I conclude with a review of the status of the calculation of light quark masses from lattice QCD.
Kallin, Catherine; Berlinsky, John
2016-05-01
Chiral superconductivity is a striking quantum phenomenon in which an unconventional superconductor spontaneously develops an angular momentum and lowers its free energy by eliminating nodes in the gap. It is a topologically non-trivial state and, as such, exhibits distinctive topological modes at surfaces and defects. In this paper we discuss the current theory and experimental results on chiral superconductors, focusing on two of the best-studied systems, Sr2RuO4, which is thought to be a chiral triplet p-wave superconductor, and UPt3, which has two low-temperature superconducting phases (in zero magnetic field), the lower of which is believed to be chiral triplet f-wave. Other systems that may exhibit chiral superconductivity are also discussed. Key signatures of chiral superconductivity are surface currents and chiral Majorana modes, Majorana states in vortex cores, and the possibility of half-flux quantum vortices in the case of triplet pairing. Experimental evidence for chiral superconductivity from μSR, NMR, strain, polar Kerr effect and Josephson tunneling experiments are discussed.
Simula, Silvano
2001-01-01
The application of relativistic constituent quark models to the evaluation of the electromagnetic properties of the nucleon and its resonances is addressed. The role of the pair creation process in the Feynmann triangle diagram is discussed and the importance both of choosing the light-front formalism and of using a Breit frame where the plus component of the four-momentum transfer is vanishing, is stressed. The nucleon elastic form factors are calculated free of spurious effects related to t...
International Nuclear Information System (INIS)
The most important particle accelerators that can contribute to quark production efforts are overviewed. The history of the discovery of quark particles is outlined. The so-called y-particles were found with 9460 MeV mass in 1977, the new particle was called beauty quark. The tau-particles were discovered in 1975. The most important features of the new generation of particles, the quark family are discussed. (R.P.)
Relativistic Chiral Theory of Nuclear Matter and QCD Constraints
Chanfray, G.; Ericson, M.
2009-01-01
Talk given by G. Chanfray at PANIC 08, Eilat (Israel), november 10-14, 2008 We present a relativistic chiral theory of nuclear matter which includes the effect of confinement. Nuclear binding is obtained with a chiral invariant scalar background field associated with the radial fluctuations of the chiral condensate Nuclear matter stability is ensured once the scalar response of the nucleon depending on the quark confinement mechanism is properly incorporated. All the parameters are fixed o...
Quark Propagation in the Quark-Gluon Plasma
Li, Xiangdong; Shakin, C M; Sun, Qing; Li, Xiangdong; Li, Hu; Sun, Qing
2004-01-01
It has recently been suggested that the quark-gluon plasma formed in heavy-ion collisions behaves as a nearly ideal fluid. That behavior may be understood if the quark and antiquark mean-free- paths are very small in the system, leading to a "sticky molasses" description of the plasma, as advocated by the Stony Brook group. This behavior may be traced to the fact that there are relatively low-energy $q\\bar{q}$ resonance states in the plasma leading to very large scattering lengths for the quarks. These resonances have been found in lattice simulation of QCD using the maximum entropy method (MEM). We have used a chiral quark model, which provides a simple representation of effects due to instanton dynamics, to study the resonances obtained using the MEM scheme. In the present work we use our model to study the optical potential of a quark in the quark-gluon plasma and calculate the quark mean-free-path. Our results represent a specific example of the dynamics of the plasma as described by the Stony Brook group...
Perturbative renormalization factors of quark operators for domain-wall QCD
Aoki, Sinya; Izubuchi, Taku; Noaki, Junichi; Kuramashi, Yoshinobu; Taniguchi, Yusuke
1999-01-01
We calculate one-loop renormalization factors of several quark operators including bilinear, three- and four-quark operator for domain-wall fermion action. Since Green functions are constructed for external physical quark fields, our renormalization method is simple and can be easily applied to calculation of any quark operators. Our results show that these renormalized quark operators preserve several chiral properties of continuum massless QCD, which can be understood by the property of ext...
A new estimate of the quark masses
International Nuclear Information System (INIS)
Assuming chiral symmetry breaking is due to a quark mass term, and some particular combinations of the lowest-lying meson states belong to the octet representation of the chiral algebra of the observable light plane charges, one finds for the bare quark masses the (approximate) formulae m(u)2 approximately equal to m(π)2/24, m(s)/m(u)=2m(k)F(k)/m(π)F(π)-1, leading to the numerical estimates m(u) approximately equal to 30MeV, m(s) approximately equal to 200MeV
Embedded monopoles in quark eigenmodes in quenched SU(2) QCD
Chernodub, M N
2006-01-01
We study the embedded QCD monopoles (``quark monopoles'') using low-lying eigenmodes of the overlap Dirac operator in zero- and finite-temperature quenched SU(2) gauge theory on the lattice. These monopoles correspond to gauge-invariant hedgehogs in the quark-antiquark condensates. The monopoles were suggested to be agents of the chiral symmetry restoration since their cores should suppress the chiral condensate. We study numerically the scalar, axial and chirally invariant definitions of the embedded monopoles and show that the monopole densities are in fact globally anti-correlated with the density of the Dirac eigenmodes. We observe, that the embedded monopoles corresponding to low-lying Dirac eigenvalues are dense in the chirally invariant (high temperature) phase and dilute in the chirally broken (low temperature) phase. We find that the scaling of the scalar and axial monopole densities towards the continuum limit is similar to the scaling of the string-like objects while the chirally invariant monopole...
Deconfinement and Chiral Restoration in Hot and Dense Matter
International Nuclear Information System (INIS)
We propose a picture that the chiral phase transition at zero quark mass and the deconfinement transition at infinite quark mass are continuously connected. This gives a simple interpretation on the coincidence of the pseudo-critical temperatures observed in lattice QCD. We discuss a possible dynamical mechanism behind the simultaneous crossovers and show the results in a model study
Energy Technology Data Exchange (ETDEWEB)
Stiele, Rainer
2014-04-28
Polyakov-loop-extended constituent-quark models are useful to investigate the chiral and (de)confinement phase structure and the thermodynamics of strongly-interacting matter. It is shown that taking into account the quark backreaction on the gauge-field dynamics as well as quantum and thermal fluctuations of quarks and mesons is crucial in such models to achieve results for order parameters and thermodynamics that are in line with non-perturbative calculations at vanishing chemical potential. The dependence of the results on remaining parameters is discussed. The investigations are extended to nonzero quark density and isospin. The impact of unquenching effects in the Polyakov-loop potential on the phase structure at non-vanishing quark densities is discussed. Predictions for thermodynamics at nonzero isospin are shown. Furthermore, the reliability of those models is tested by confronting its results with lattice data on the isospin dependence of the transition temperature. The phase structure of the three-dimensional temperature-isospin-quark density phase diagram is investigated. Moreover, the process of nucleation at small temperatures and large densities is investigated and the surface tension for the phase transition calculated. Some consequences of the results for the early Universe, for heavy-ion collisions, and for proto-neutron stars are discussed.
Metastable strange matter and compact quark stars
Malheiro, M; Taurines, A R
2003-01-01
Strange quark matter in beta equilibrium at high densities is studied in a quark confinement model. Two equations of state are dynamically generated for the {\\it same} set of model parameters used to describe the nucleon: one corresponds to a chiral restored phase with almost massless quarks and the other to a chiral broken phase. The chiral symmetric phase saturates at around five times the nuclear matter density. Using the equation of state for this phase, compact bare quark stars are obtained with radii and masses in the ranges $R\\sim 5 - 8$ km and $M\\sim M_\\odot$. The energy per baryon number decreases very slowly from the center of the star to the periphery, remaining above the corresponding values for the iron or the nuclear matter, even at the edge. Our results point out that strange quark matter at very high densities may not be absolutely stable and the existence of an energy barrier between the two phases may prevent the compact quarks stars to decay to hybrid stars.
Quarks, gluons and the spin of the proton
International Nuclear Information System (INIS)
Experimentally, quark helicities do not seem to contribute to the proton spin. I shall show how this result can be obtained by a direct computation in a chiral field-theoretical model of quark and gluon confinement, taking gluon-exchange effects into account. At the same time, I shall get an estimate for the gluon-helicity contribution
Tung, Kwong-Kwai Humphrey
1992-01-01
recoil problem. The validity of the heavy-quark symmetries in Bto K^* is also discussed. The quark model suggests the same symmetries even though the constituent s quark of K^* is not heavy.
Kao, Chung Wen
2011-01-01
We investigate the chiral restoration at finite temperature $(T)$ under the strong external magnetic field $\\vec{B}=B_{0}\\hat{z}$ of the SU(2) light-flavor QCD matter. We employ the instanton-liquid QCD vacuum configuration accompanied with the linear Schwinger method for inducing the magnetic field. The Harrington-Shepard caloron solution is used to modify the instanton parameters, i.e. the average instanton size $(\\bar{\\rho})$ and inter-instanton distance $(\\bar{R})$, as functions of $T$. In addition, we include the meson-loop corrections (MLC) as the large-$N_{c}$ corrections because they are critical for reproducing the universal chiral restoration pattern. We present the numerical results for the constituent-quark mass as well as chiral condensate which signal the spontaneous breakdown of chiral-symmetry (SB$\\chi$S), as functions of $T$ and $B$. Besides we find that the changes for the $F_\\pi$ and $m_\\pi$ due to the magnetic field is relatively small, in comparison to those caused by the finite $T$ effec...
How tetraquarks can generate a second chiral phase transition
Pisarski, Robert D
2016-01-01
We consider how tetraquarks can affect the chiral phase transition in theories like QCD, with light quarks coupled to three colors. For two flavors the tetraquark field is an isosinglet, and its effect is minimal. For three flavors, however, the tetraquark field transforms in the same representation of the chiral symmetry group as the usual chiral order parameter, and so for very light quarks there may be two chiral phase transitions, which are both of first order. In QCD, results from the lattice indicate that any transition from the tetraquark condensate is a smooth crossover. In the plane of temperature and quark chemical potential, though, a crossover line for the tetraquark condensate is naturally related to the transition line for color superconductivity. For four flavors we suggest that a triquark field, antisymmetric in both flavor and color, combine to form hexaquarks.
Chiral Langrangian with confinement from the QCD Langrangian
Energy Technology Data Exchange (ETDEWEB)
Yu A. Simonov
2002-01-01
An effective Langrangian for the light quark in the field of a static source is derived systematically using the exact field correlator expansion. The lowest Gaussian term is bosonized using nonlocal colorless bosonic fields and a general structure of effective chiral Langrangian is obtained containing all set of fields. The new and crucial result is that the condensation of scalar isoscalar field which is a usual onset of chiral symmetry breaking and is constant in space-time, assumes here the form of the confining string and contributes to the confining potential while the rest bosonic fields describe mesons with the q{rvec q} quark structure and pseudoscalars play the role of Nambu-Goldstone fields. Using derivative expansion the effective chiral Langrangian is deduced containing both confinement and chiral effects for heavy-light mesons. The pseudovector quark coupling constant is computed to be exactly unity in the local limit in agreement with earlier large N{sub c} arguments.
Quark-Antiquark Condensates in the Hadronic Phase
Tawfik, A
2005-01-01
We use a hadron resonance gas model to calculate the quark-antiquark condensates for light (up and down) and strange quark flavors at finite temperatures and chemical potentials. At zero chemical potentials, we find that at the temperature where the light quark-antiquark condensates entirely vanish the strange quark-antiquark condensate still keeps a relatively large fraction of its value in the vacuum. This is in agreement with results obtained in lattice simulations and in chiral perturbation theory at finite temperature and zero chemical potentials. Furthermore, we find that this effect slowly disappears at larger baryon chemical potential. These results might have significant consequences for our understanding of QCD at finite temperatures and chemical potentials. Concretely, our results imply that there might be a domain of temperatures where chiral symmetry is restored for light quarks, but still broken for strange quark that persists at small chemical potentials. This might have practical consequences ...
NJL model approach to diquarks and baryons in quark matter
Blaschke, D.; Dubinin, A.; Zablocki, D.
2015-01-01
We describe baryons as quark-diquark bound states at finite temperature and density within the NJL model for chiral symmetry breaking and restoration in quark matter. Based on a generalized Beth-Uhlenbeck approach to mesons and diquarks we present in a first step the thermodynamics of quark-diquark matter which includes the Mott dissociation of diquarks at finite temperature. In a second step we solve the Bethe-Salpeter equation for the baryon as a quark-diquark bound state in quark-diquark m...
Energy Technology Data Exchange (ETDEWEB)
Floss, H.G. [Univ. of Washington, Seattle, WA (United States)
1994-12-01
This paper deals with compounds that are chiral-at least in part, due to isotope substitution-and their use in tracing the steric course of enzyme reaction in vitro and in vivo. There are other applications of isotopically chiral compounds (for example, in analyzing the steric course of nonenzymatic reactions and in probing the conformation of biomolecules) that are important but they will not be discussed in this context.
Chiral symmetry breaking and chiral polarization: Tests for finite temperature and many flavors
Directory of Open Access Journals (Sweden)
Andrei Alexandru
2015-02-01
Full Text Available It was recently conjectured that, in SU(3 gauge theories with fundamental quarks, valence spontaneous chiral symmetry breaking is equivalent to condensation of local dynamical chirality and appearance of chiral polarization scale Λch. Here we consider more general association involving the low-energy layer of chirally polarized modes which, in addition to its width (Λch, is also characterized by volume density of participating modes (Ω and the volume density of total chirality (Ωch. Few possible forms of the correspondence are discussed, paying particular attention to singular cases where Ω emerges as the most versatile characteristic. The notion of finite-volume “order parameter”, capturing the nature of these connections, is proposed. We study the effects of temperature (in Nf=0 QCD and light quarks (in Nf=12, both in the regime of possible symmetry restoration, and find agreement with these ideas. In Nf=0 QCD, results from several volumes indicate that, at the lattice cutoff studied, the deconfinement temperature Tc is strictly smaller than the overlap–valence chiral transition temperature Tch in real Polyakov line vacuum. Somewhat similar intermediate phase (in quark mass is also seen in Nf=12. It is suggested that deconfinement in Nf=0 is related to indefinite convexity of absolute X-distributions.
Wess-Zumino-Witten action and photons from the Chiral Magnetic Effect
Fukushima, Kenji; Mameda, Kazuya
2012-01-01
We revisit the Chiral Magnetic Effect (CME) using the chiral Lagrangian. We demonstrate that the electric-current formula of the CME is derived immediately from the contact part of the Wess-Zumino-Witten action. This implies that the CME could be, if observed, a signature for the local parity violation, but a direct evidence for neither quark deconfinement nor chiral restoration. We also discuss the reverse Chiral Magnetic Primakoff Effect, i.e. the real photon production through the vertex a...
Possible $\\Delta\\Delta$ dibaryons in the quark cluster model
Q. B. Li; Shen, P. N.
1999-01-01
In the framework of RGM, the binding energy of one channel $\\Delta\\Delta_{(3,0)}$($d^*$) and $\\Delta\\Delta_{(0,3)}$ are studied in the chiral SU(3) quark cluster model. It is shown that the binding energies of the systems are a few tens of MeV. The behavior of the chiral field is also investigated by comparing the results with those in the SU(2) and the extended SU(2) chiral quark models. It is found that the symmetry property of the $\\Delta\\Delta$ system makes the contribution of the relativ...
Constant gluon propagator and quark confinement in QCD
International Nuclear Information System (INIS)
Schwinger-Dyson equation for quark propagator in QCD is investigated in the infrared region. Gauge identity is taken into account. It is shown that the infrared behaviour of the gluon propagator in the covariant gauge D(K)approxδ(K) leads to the quark confinement. All the obtained solutions for quark propagator are of the confinement type, have a nonperturbative character and do not break chiral invariance
Chiral symmetry breaking in QCD Lite
Engel, Georg P; Lottini, Stefano; Sommer, Rainer
2014-01-01
A distinctive feature of the presence of spontaneous chiral symmetry breaking in QCD is the condensation of low modes of the Dirac operator near the origin. The rate of condensation must be equal to the slope of (Mpi^2 Fpi^2)/2 with respect to the quark mass m in the chiral limit, where Mpi and Fpi are the mass and the decay constant of the Nambu-Goldstone bosons. We compute the spectral density of the (Hermitian) Dirac operator, the quark mass, the pseudoscalar meson mass and decay constant by numerical simulations of lattice QCD with two light degenerate Wilson quarks. We use CLS lattices at three values of the lattice spacing in the range 0.05-0.08 fm, and for several quark masses corresponding to pseudoscalar mesons masses down to 190 MeV. Thanks to this coverage of parameters space, we can extrapolate all quantities to the chiral and continuum limits with confidence. The results show that the low quark modes do condense in the continuum as expected by the Banks-Casher mechanism, and the rate of condensat...
''Follow that quark!'' (and other exclusive stories)
International Nuclear Information System (INIS)
Quarks are considered to be the basic constituents of matter. In a series of recent experiments, Carroll studied exclusive reactions as a means of determining the interactions between quarks. Quantum Chromo-dynamics (QCD) is the modern theory of the interaction of quarks. This theory explains how quarks are held together via the strong interaction in particles known as hadrons. Hadrons consisting of three quarks are called baryons. Hadrons made up of a quark and an antiquark are called mesons. In his lecture, Carroll describes what happens when two hadrons collide and scatter to large angles. The violence of the collision causes the gluons that bind the quarks in a particular hadron to temporarily lose their grip on particular quarks. Quarks scramble toward renewed unity with other quarks, and they undergo rearrangement, which generally results in additional new particles. A two-body exclusive reaction has occurred when the same number of particles exist before and after the collisions. At large angles these exclusive reactions are very rare. The labels on the quarks known as flavor enable the experimenter to follow the history of individual quarks in detail during these exclusive reactions. Carroll describes the equipment used in the experiment to measure short distance, hard collisions at large angles. The collisions he discusses occur when a known beam of mesons or protons collide with a stationary proton target. Finally, Carroll summarizes what the experiments have shown from the study of exclusive reactions and what light some of their results shed on the theory of QCD
Single quark entropy and the Polyakov loop
Weber, Johannes Heinrich
2016-01-01
We study Quantum Chromodynamics (QCD) with 2+1 flavors with almost physical quark masses using the highly improved staggered quark action (HISQ). We calculate the Polyakov loop in a wide temperature range, obtain the free energy and the entropy of a single static quark and discuss the QCD crossover region in detail. We show that the entropy has a peak close to the chiral crossover and consider the consequences for the deconfinement aspects of the crossover phenomena. We study the renormalized Polyakov loop susceptibilities and place them into the context of the crossover. We also obtain a quantitative result for the onset of weak coupling behavior at high temperatures.
The Phase Structure of the Polyakov--Quark-Meson Model
Schaefer, Bernd-Jochen; Pawlowski, Jan M.; Wambach, Jochen
2007-01-01
The relation between the deconfinement and chiral phase transition is explored in the framework of an Polyakov-loop-extended two-flavor quark-meson (PQM) model. In this model the Polyakov loop dynamics is represented by a background temporal gauge field which also couples to the quarks. As a novelty an explicit quark chemical potential and N_f-dependence in the Polyakov loop potential is proposed by using renormalization group arguments. The behavior of the Polyakov loop as well as the chiral...
Are quarks and leptons composite
International Nuclear Information System (INIS)
This chapter examines composite quarks and leptons by starting with generalities and gradually concentrating on the specific example of the rishon model. Assumes that the standard model is a valid theory of quarks, leptons and their interactions. Discusses the various open problems which remain, even if the standard model is accepted. Reviews the pros and cons of the several possible solutions which exist for each of the open problems (e.g., grand unification, technicolor, horizontal symmetries, supersymmetry, composite quarks and leptons). Attempts to find a simple realistic model for composite quarks and leptons. Offers the following line of reasoning: 1) assume the standard model; 2) show a need to go beyond it; 3) consider different classes of ideas; 4) concentrate on the notion of compositeness; 5) study its general difficulties, mainly the scale problem; 6) assume a connection between composite massless fermions and an unbroken chiral symmetry; 7) establish a general framework based on hypercolor and a chiral symmetry; 8) establish the general requirements for a candidate model; 9) find the minimal scheme; and 10) study it and discover its successes and failures
Chiral symmetry restoration in effective Lagrangian models
International Nuclear Information System (INIS)
The restoration is studied of chiral symmetry in dense baryon matter using effective lagrangian models of QCD, in which baryons are described as topological solitons. Starting from the breaking of scale invariance and chiral symmetry in the QCD vacuum, the foundations are discussed of effective lagrangians and their relevance for applications to dense matter. Soliton models, such a the Skyrme model, show a phase transition at high densities, whose order parameter is the average scalar field. The properties are investigated of the two phases of the effective theory and show that the phase transition corresponds to the restoration of the chiral symmetry of QCD. It is argued that it should not be understood as deconfinement. The author then considers this phase transition in the context of the Cheshire Cat principle, which provides the link to the underlying quarks of QCD. An analogue of the Cheshire Cat property of this chiral bag model for baryons is found in solitons of effective lagrangians with a scalar glueball field. The Cheshire Cat interpretation of the results of effective lagrangians provides a consistent picture of chiral symmetry restoration at high densities. To verify this interpretation explicitly, the author finally generalizes the effective lagrangian approach to dense matter to a chiral bag model description with quark degrees of freedom
Staggered heavy baryon chiral perturbation theory
Bailey, Jon A.
2008-03-01
Although taste violations significantly affect the results of staggered calculations of pseudoscalar and heavy-light mesonic quantities, those entering staggered calculations of baryonic quantities have not been quantified. Here I develop staggered chiral perturbation theory in the light-quark baryon sector by mapping the Symanzik action into heavy baryon chiral perturbation theory. For 2+1 dynamical quark flavors, the masses of flavor-symmetric nucleons are calculated to third order in partially quenched and fully dynamical staggered chiral perturbation theory. To this order the expansion includes the leading chiral logarithms, which come from loops with virtual decuplet-like states, as well as terms of O(mπ3), which come from loops with virtual octet-like states. Taste violations enter through the meson propagators in loops and tree-level terms of O(a2). The pattern of taste symmetry breaking and the resulting degeneracies and mixings are discussed in detail. The resulting chiral forms are appropriate to lattice results obtained with operators already in use and could be used to study the restoration of taste symmetry in the continuum limit. I assume that the fourth root of the fermion determinant can be incorporated in staggered chiral perturbation theory using the replica method.
Strangeness at high temperatures: from hadrons to quarks.
Bazavov, A; Ding, H-T; Hegde, P; Kaczmarek, O; Karsch, F; Laermann, E; Maezawa, Y; Mukherjee, Swagato; Ohno, H; Petreczky, P; Schmidt, C; Sharma, S; Soeldner, W; Wagner, M
2013-08-23
Appropriate combinations of up to fourth order cumulants of net strangeness fluctuations and their correlations with net baryon number and electric charge fluctuations, obtained from lattice QCD calculations, have been used to probe the strangeness carrying degrees of freedom at high temperatures. For temperatures up to the chiral crossover, separate contributions of strange mesons and baryons can be well described by an uncorrelated gas of hadrons. Such a description breaks down in the chiral crossover region, suggesting that the deconfinement of strangeness takes place at the chiral crossover. On the other hand, the strangeness carrying degrees of freedom inside the quark gluon plasma can be described by a weakly interacting gas of quarks only for temperatures larger than twice the chiral crossover temperature. In the intermediate temperature window, these observables show considerably richer structures, indicative of the strongly interacting nature of the quark gluon plasma. PMID:24010429
From enemies to friends: chiral symmetry on the lattice
International Nuclear Information System (INIS)
The physics of strong interactions is invariant under the exchange of left-handed and right-handed quarks, at least in the massless limit. This invariance is reflected in the chiral symmetry of quantum chromodynamics. Surprisingly, it has become clear only recently how to implement this important symmetry in lattice formulations of quantum field theories. We will discuss realizations of exact lattice chiral symmetry and give an example of the computation of a physical observable in quantum chromodynamics where chiral symmetry is important. This calculation is performed by relying on finite size scaling methods as predicted by chiral perturbation theory. (orig.)
A Diquark-Quark Model with Its Use in Nucleon Form Factors
Institute of Scientific and Technical Information of China (English)
WANG Hong-Min; ZHANG Ben-Ai
2005-01-01
The nucleon electromagnetic form factors are investigated within a simple diquark-quark model using the light-front formalism. In this model, baryon is described as a bound state of one quark and one clustering diquark.The calculational results are compared with the experimental ones. We also regard the quarks in a baryon as pointlike constituent quarks.
Quark phase-space distributions and orbital angular momentum
Cédric LorcéOrsay, IPN and Orsay, LPT; Barbara Pasquini(Pavia U. and INFN, Pavia)
2012-01-01
We discuss the Wigner functions of the nucleon which provide multi-dimensional images of the quark distributions in phase space. They combine in a single picture all the information contained in the generalized parton distributions (GPDs) and the transverse-momentum dependent parton distributions (TMDs). In particular, we present results for the distribution of unpolarized quarks in a longitudinally polarized nucleon obtained in a light-cone constituent quark model. We show how quark orbital ...
Quark matter symmetry energy and quark stars
Chu, Peng-Cheng; Chen, Lie-Wen
2012-01-01
We extend the confined-density-dependent-mass (CDDM) model to include isospin dependence of the equivalent quark mass. Within the confined-isospin-density-dependent-mass (CIDDM) model, we study the quark matter symmetry energy, the stability of strange quark matter, and the properties of quark stars. We find that including isospin dependence of the equivalent quark mass can significantly influence the quark matter symmetry energy as well as the properties of strange quark matter and quark sta...
Quark fragmentation into spin-triplet $S$-wave quarkonium
Bodwin, Geoffrey T; Kim, U-Rae; Lee, Jungil
2014-01-01
We compute fragmentation functions for a quark to fragment to a quarkonium through an $S$-wave spin-triplet heavy quark-antiquark pair. We consider both color-singlet and color-octet heavy quark-antiquark ($Q\\bar Q$) pairs. We give results for the case in which the fragmenting quark and the quark that is a constituent of the quarkonium have different flavors and for the case in which these quarks have the same flavors. Our results for the sum over all spin polarizations of the $Q\\bar Q$ pairs confirm previous results. Our results for longitudinally polarized $Q\\bar Q$ pairs are new.
Gleiser, Marcelo; Thorarinson, Joel; Walker, Sara Imari
2008-12-01
Most biomolecules occur in mirror, or chiral, images of each other. However, life is homochiral: proteins contain almost exclusively L-amino acids, while only D-sugars appear in RNA and DNA. The mechanism behind this fundamental asymmetry of life remains an open problem. Coupling the spatiotemporal evolution of a general autocatalytic polymerization reaction network to external environmental effects, we show through a detailed statistical analysis that high intensity and long duration events may drive achiral initial conditions towards chirality. We argue that life’s homochirality resulted from sequential chiral symmetry breaking triggered by environmental events, thus extending the theory of punctuated equilibrium to the prebiotic realm. Applying our arguments to other potentially life-bearing planetary platforms, we predict that a statistically representative sampling will be racemic on average.
Gleiser, Marcelo; Walker, Sara Imari
2008-01-01
Most biomolecules occur in mirror, or chiral, images of each other. However, life is homochiral: proteins contain almost exclusively levorotatory (L) amino acids, while only dextrorotatory (R) sugars appear in RNA and DNA. The mechanism behind this fundamental asymmetry of life remains an open problem. Coupling the spatiotemporal evolution of a general autocatalytic polymerization reaction network to external environmental effects, we show through a detailed statistical analysis that high intensity and long duration events may drive achiral initial conditions towards chirality. We argue that life's homochirality resulted from sequential chiral symmetry breaking triggered by environmental events, thus extending the theory of punctuated equilibrium to the prebiotic realm. Applying our arguments to other potentially life-bearing planetary platforms, we predict that a statistically representative sampling will be racemic on average.
Chiral Magnetic Effect in Heavy Ion Collisions
Liao, Jinfeng
2016-01-01
The Chiral Magnetic Effect (CME) is a remarkable phenomenon that stems from highly nontrivial interplay of QCD chiral symmetry, axial anomaly, and gluonic topology. It is of fundamental importance to search for the CME in experiments. The heavy ion collisions provide a unique environment where a hot chiral-symmetric quark-gluon plasma is created, gluonic topological fluctuations generate chirality imbalance, and very strong magnetic fields $|\\vec{\\bf B}|\\sim m_\\pi^2$ are present during the early stage of such collisions. Significant efforts have been made to look for CME signals in heavy ion collision experiments. In this contribution we give a brief overview on the status of such efforts.
Chang, N P
1994-01-01
Chiral symmetry undergoes a metamorphosis at T.sub(c). For T < T.sub(c), the usual Noether charge, \\Qa, is dynamically broken by the vacuum. Above T.sub(c), chiral symmetry undergoes a subtle change, and the Noether charge \\underline{{\\em morphs}} into \\Qbeta, with the thermal vacuum now becoming invariant under \\Qbeta. This vacuum is however not invariant under the old \\Qa transformations. As a result, the pion remains strictly massless at high T. The pion propagates in the early universe with a halo. New order parameters are proposed to probe the structure of the new thermal vacuum.
International Nuclear Information System (INIS)
Color transparency is the vanishing of initial and final state interactions, predicted by QCD to occur in high momentum transfer quasielastic nuclear reactions. For specific reactions involving nucleons, the initial and final state interactions are expected to be dominated by exchanges of pions. We argue that these interactions are also suppressed in high momentum transfer nuclear quasielastic reactions; this is open-quotes chiral transparency.close quotes We show that studies of the e3He→e'Δ++nn reaction could reveal the influence of chiral transparency. copyright 1997 The American Physical Society
Topological and non-topological solutions in the 3-phase model of hybrid chiral bag
Sveshnikov, K; Khalili, M; Fedorov, S M; Malakhov, Il.
2002-01-01
The 3-phase version of the hybrid chiral bag model, containing the phase of asymptotic freedom, the hadronization phase as well as the intermediate phase of constituent quarks, is proposed. For this model the self-consistent solutions, which take into account the fermion vacuum polarization effects, are found in 1+1 D. The renormalized total energy of the bag is studied as a function of its geometry and topological (baryon) number. It is shown that in the case of non-zero topological charge there exists a set of configurations being the local minima of the total energy of the bag and containing all the three phases, while in the non-topological case the minimum of the total energy of the bag corresponds to vanishing size of the phase of asymptotic freedom.
Some aspects of pion physics in the Nambu- and Jona-Lasinio model and chiral Lagrangians
International Nuclear Information System (INIS)
I discuss here to what extent the original two-flavour NJL model (which has a minimal number of adjustable parameters) reproduces pion observables. In particular, the sensitivity of the recently calculated electromagnetic mass shift to these NJL parameters is pointed out and a new way to fix them is suggested. A new set of O(1/Nc) diagrams, which are the first meson loop corrections to the RPA, is presented and its effect on the pionic Goldstone mode, its electromagnetic form factor, weak decay constant, and on the constituent quark mass m is discusseed. The relation of these NJL model results to some other chiral Lagrangians is pointed out, where ever possible. The here presented higher order diagrams indicate how one could systematically generate the next-order diagrams. It is, however, questionable whether the simplistic but mathematically manageable contact interaction of the NJL model should be maintained also in these higher order diagrams. (orig.)
Surface tension in the cold and dense chiral transition and astrophysical applications
Palhares, L F
2011-01-01
The surface tension of cold and dense QCD phase transitions has appeared recently as a key ingredient in different astrophysical scenarios, ranging from core-colapse supernovae explosions to compact star structure. If the surface tension is low enough, observable consequences are possible. Its value is however not known from first-principle methods in QCD, calling for effective approaches. Working within the framework of homogeneous nucleation by Langer, we discuss the steps that are needed to obtain the nucleation parameters from a given effective potential. As a model for deriving the effective potential for the chiral transition, we adopt the linear sigma model with constituent quarks at very low temperatures, which provides an effective description for the thermodynamics of the strong interaction in cold and dense matter, and predict a surface tension of Sigma ~ 5--15 MeV/fm^2, well below previous estimates. Including temperature effects and vacuum logarithmic corrections, we find a clear competition betw...
Chiral hybrid bag model with the boson field inside the bag
International Nuclear Information System (INIS)
The three-phase version of the hybrid chiral bag model, containing the phase of asymptotic freedom, the hadronization phase as well as the intermediate phase of constituent quarks, is proposed. For this model the self-consistent solution, which takes into account the fermion vacuum polarization effects, is found in (1+1) D. Within this solution the total energy of the bag, including the one-loop contribution from the Dirac's sea, is studied as the function of the bag geometry under condition of nonvanishing boson condensate density in the interior region. The existence and uniqueness of the ground state bag configuration, which minimizes the total energy and contains all the three phases, are shown. (author)
Connections between chiral Lagrangians and QCD sum-rules
Fariborz, Amir H.; Pokraka, A.; Steele, T. G.
2016-01-01
In this paper, it is shown how a chiral Lagrangian framework can be used to derive relationships connecting quark-level QCD correlation functions to mesonic-level two-point functions. Crucial ingredients of this connection are scale factor matrices relating each distinct quark-level substructure (e.g. quark-antiquark, four-quark) to its mesonic counterpart. The scale factors and mixing angles are combined into a projection matrix to obtain the physical (hadronic) projection of the QCD correlation function matrix. Such relationships provide a powerful bridge between chiral Lagrangians and QCD sum-rules that are particularly effective in studies of the substructure of light scalar mesons with multiple complicated resonance shapes and substantial underlying mixings. The validity of these connections is demonstrated for the example of the isotriplet a0(980)-a0(1450) system, resulting in an unambiguous determination of the scale factors from the combined inputs of QCD sum-rules and chiral Lagrangians. These scale factors lead to a remarkable agreement between the quark condensates in QCD and the mesonic vacuum expectation values that induce spontaneous chiral symmetry breaking in chiral Lagrangians. This concrete example shows a clear sensitivity to the underlying a0-system mixing angle, illustrating the value of this methodology in extensions to more complicated mesonic systems.
Quark mass deformation of holographic massless QCD
International Nuclear Information System (INIS)
We propose several quark mass deformations of the holographic model of massless QCD using the D4/D8/D8-bar-brane configuration proposed by Sakai and Sugimoto. The deformations are based on introducing additional D4- or D6-branes away from the QCD D4-branes. The idea is similar to extended technicolor theories, where the chiral symmetry breaking by additional D-branes is mediated to QCD to induce non-zero quark masses. In the D-brane picture, as well as the holographic dual gravity description, the quark and the pion masses are generated by novel worldsheet instantons with finite area. We also derive the Gell-Mann-Oakes-Renner relation, and find the value of the chiral condensate in the Sakai-Sugimoto model. (author)
International Nuclear Information System (INIS)
The suggestion by Jaffe that if σ is a light q2q-bar2 state 0++ then even the fundamental chiral transformation properties of the σ becomes unclear, has stimulated much interest. Adler pointed out that in fact the seminal work on chiral symmetry via PCAC consistency, is really quite consistent with the σ being predominantly q2q-bar2. This interpretation was actually backed by subsequent work on effective Lagrangian methods for linear and non linear realizations. More recent work of Achasov suggests that intermediate four-quark states determine amplitudes involving other scalars a0(980) and f0(980) below 1 GeV, and the report by Ning Wu that study on σ meson in J/ψ → ωπ+π- continue to support a non qq-bar σ with mass as low as 390 MeV. It is also noted that more recent re-analysis of πK scattering by S. Ishida et al. together with the work of the E791 Collaboration, support the existence of the scalar κ particle with comparatively light mass as well
Chiral Nanoscience and Nanotechnology
Dibyendu S. Bag; T.C. Shami; K.U. Bhasker Rao
2008-01-01
The paper reviews nanoscale science and technology of chiral molecules/macromolecules-under twosubtopics-chiral nanotechnology and nano-chiral technology. Chiral nanotechnology discusses thenanotechnology, where molecular chirality plays a role in the properties of materials, including molecularswitches, molecular motors, and other molecular devices; chiral supramolecules and self-assembled nanotubesand their functions are also highlighted. Nano-chiral technology describes the nanoscale appr...
Schwinger-Dyson equations: Dynamical Chiral Symmetry Breaking and Confinement
Roberts, Craig D.(Physics Division, Argonne National Laboratory, Argonne, IL, 60439, USA)
1993-01-01
A representative but not exhaustive review of the Schwinger-Dyson equation (SDE) approach to the nonperturbative study of QCD is presented. The main focus is the SDE for the quark self energy but studies of the gluon propagator and quark-gluon vertex are also discussed insofar as they are important to the quark SDE. The scope of this article is the application of these equations to the study of dynamical chiral symmetry breaking, quark confinement and the phenomenology of the spectrum and dyn...
Topological Susceptibility with Three Flavors of Staggered Quarks
International Nuclear Information System (INIS)
As one test of the validity of the staggered-fermion fourth-root determinant trick, we examine the suppression of the topological susceptibility of the QCD vacuum in the limit of small quark mass. The suppression is sensitive to the number of light sea quark flavors. Our study is done in the presence of 2+1 flavors of dynamical quarks in the improved staggered fermion formulation. Variance-reduction techniques provide better control of statistical errors. New results from staggered chiral perturbation theory account for taste-breaking effects in the low-quark mass behavior of the susceptibility, thereby reducing scaling violations from this source. Measurements over a range of quark masses at two lattice spacings permit a rough continuum extrapolation to remove the remaining lattice artifacts. The results are consistent with chiral perturbation theory with the correct flavor counting
Topological susceptibility with three flavors of staggered quarks
Aubin, C; Billeter, B; DeTar, C; Gottlieb, S; Gregory, E; Heller, U M; Hetrick, J E; Osborn, J; Sugar, R L; Toussaint, D; Billeter, Brian; Gottlieb, Steven
2005-01-01
As one test of the validity of the staggered-fermion fourth-root determinant trick, we examine the suppression of the topological susceptibility of the QCD vacuum in the limit of small quark mass. The suppression is sensitive to the number of light sea quark flavors. Our study is done in the presence of 2+1 flavors of dynamical quarks in the improved staggered fermion formulation. Variance-reduction techniques provide better control of statistical errors. New results from staggered chiral perturbation theory account for taste-breaking effects in the low-quark mass behavior of the susceptibility, thereby reducing scaling violations from this source. Measurements over a range of quark masses at two lattice spacings permit a rough continuum extrapolation to remove the remaining lattice artifacts. The results are consistent with chiral perturbation theory with the correct flavor counting.
Hashimoto, Koji; Yoshida, Kentaroh
2016-01-01
Assigning a chaos index for vacua of generic quantum field theories is a challenging problem. We find chaotic behavior of chiral condensates of a quantum gauge theory at strong coupling limit, by using the AdS/CFT correspondence. We evaluate the time evolution of homogeneous quark condensates and in an N=2 supersymmetric QCD with the SU(N_c) gauge group at large N_c and at large 't Hooft coupling lambda. At an equivalent classical gravity picture, a Lyapunov exponent is readily defined. We show that the condensates exhibit chaotic behavior for energy density E > (6x10^2) (N_c/lambda^2) (m_q)^4 where m_q is the quark mass. The energy region of the chaotic vacua of the N=2 supersymmetric QCD increases for smaller N_c or larger lambda. The Lyapunov exponent is calculated as a function of the theory (N_c,lambda,E), showing that the N=2 supersymmetric QCD is more chaotic for smaller N_c.
Quark-Model Predictions for Axial Charges of Nucleon and N* Resonances
Directory of Open Access Journals (Sweden)
Wagenbrunn R.F.
2010-04-01
Full Text Available We have investigated the axial charges of the nucleon and N* resonances in a relativistic framework. Besides the axial charge of the nucleon, ﬁrst predictions are reported for the axial charges of all well-established N* resonances below ∼1.9 GeV as produced by the relativistic constituent quark models relying on Goldstoneboson-exchange and one-gluon-exchange hyperﬁne interactions. The results for the axial charge of the nucleon are found close to experiment but with somewhat smaller values, similar to modern ﬁndings from quantum chromodynamics on the lattice. The predictions of the axial charges of the negative-parity N* (1535 and N*(1650 resonances also agree with what has most recently become available from lattice calculations. We discuss the roles of the axial charges of the N* resonances for the phenomenon of chiral-symmetry restoration possibly occurring in the higher hadron spectra.
The Chiral Magnetic Effect and Anomaly-Induced Transport
Kharzeev, Dmitri E
2013-01-01
The Chiral Magnetic Effect (CME) is the phenomenon of electric charge separation along the external magnetic field that is induced by the chirality imbalance. The CME is a macroscopic quantum effect - it is a manifestation of the chiral anomaly creating a collective motion in Dirac sea. Because the chirality imbalance is related to the global topology of gauge fields, the CME current is topologically protected and hence non-dissipative even in the presence of strong interactions. As a result, the CME and related quantum phenomena affect the hydrodynamical and transport behavior of systems possessing chiral fermions, from the quark-gluon plasma to chiral materials. The goal of the present review is to provide an elementary introduction into the main ideas underlying the physics of CME, a historical perspective, and a guide to the rapidly growing literature on this topic.
Chiral medium produced by parallel electric and magnetic fields
Ruggieri, Marco; Chernodub, Maxim
2016-01-01
We compute (pseudo)critical temperature, $T_c$, of chiral symmetry restoration for quark matter in the background of parallel electric and magnetic fields. This field configuration leads to the production of a chiral medium on a time scale $\\tau$, characterized by a nonvanishing value of the chiral density that equilibrates due to microscopic processes in the thermal bath. We estimate the relaxation time $\\tau$ to be about $\\approx 0.1-1$ fm/c around the chiral crossover; then we compute the effect of the fields and of the chiral medium on~$T_c$. We find $T_c$ to be lowered by the external fields in the chiral medium.
Chiral spiral induced by a strong magnetic field
Abuki, H
2016-01-01
We study the modification of the chiral phase structure of QCD due to an external magnetic field. We first demonstrate how the effect of magnetic field can systematically be incorporated into a generalized Ginzburg-Landau framework. We then analyze the phase structure in the vicinity of the chiral critical point. In the chiral limit, the effect is found to be so drastic that it totally washes the tricritical point out of the phase diagram, bringing the continent for the chiral spiral. This is the case no matter how small is the intensity of the magnetic field. On the other hand, the current quark mass protects the chiral critical point from a weak magnetic field. However the critical point will eventually be covered by the chiral spiral phase as the magnetic field grows.
Renormalisation constants of quark bilinears in lattice QCD with four dynamical Wilson quarks
Blossier, B; Carrasco, N; Dimopoulos, P; Du, X; Frezzotti, R; Gimenez, V; Herdoiza, G; Jansen, K; Lubicz, V; Palao, D; Pallante, E; Pene, O; Petrov, K; Reker, S; Rossi, G C; Sanfilippo, F; Scorzato, L; Simula, S; Urbach, C
2011-01-01
We present preliminary results of the non-perturbative computation of the RI-MOM renormalisation constants in a mass-independent scheme for the action with Iwasaki glue and four dynamical Wilson quarks employed by ETMC. Our project requires dedicated gauge ensembles with four degenerate sea quark flavours at three lattice spacings and at several values of the standard and twisted quark mass parameters. The RI-MOM renormalisation constants are obtained from appropriate O(a) improved estimators extrapolated to the chiral limit.
Nucleon form factors. Probing the chiral limit
International Nuclear Information System (INIS)
The electromagnetic form factors provide important hints for the internal structure of the nucleon and continue to be of major interest for experimentalists. For an intermediate range of momentum transfers the form factors can be calculated on the lattice. However, reliability of the results is limited by systematic errors due to the required extrapolation to physical quark masses. Chiral effective field theories predict a rather strong quark mass dependence in a range which was yet unaccessible for lattice simulations. We give an update on recent results from the QCDSF collaboration using gauge configurations with Nf=2, non-perturbatively O(a)-improved Wilson fermions at very small quark masses down to 340 MeV pion mass, where we start to probe the relevant quark mass region. (orig.)
Nucleon form factors. Probing the chiral limit
Energy Technology Data Exchange (ETDEWEB)
Goeckeler, M. [Regensburg Univ. (Germany). Inst. fuer Theoretische Physik; Haegler, P. [Technische Univ. Muenchen, Garching (Germany). Physik-Dept.; Horsley, R. [Edinburgh Univ. (GB). School of Physics] (and others)
2006-10-15
The electromagnetic form factors provide important hints for the internal structure of the nucleon and continue to be of major interest for experimentalists. For an intermediate range of momentum transfers the form factors can be calculated on the lattice. However, reliability of the results is limited by systematic errors due to the required extrapolation to physical quark masses. Chiral effective field theories predict a rather strong quark mass dependence in a range which was yet unaccessible for lattice simulations. We give an update on recent results from the QCDSF collaboration using gauge configurations with Nf=2, non-perturbatively O(a)-improved Wilson fermions at very small quark masses down to 340 MeV pion mass, where we start to probe the relevant quark mass region. (orig.)
Chiral superfluidity for the heavy ion collisions
Energy Technology Data Exchange (ETDEWEB)
Kalaydzhyan, T. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Institute of Theoretical and Experimental Physics, Moscow (Russian Federation)
2013-02-15
We argue that the strongly coupled quark-gluon plasma formed at LHC and RHIC can be considered as a chiral superfluid. The ''normal'' component of the fluid is the thermalized matter in common sense, while the ''superfluid'' part consists of long wavelength (chiral) fermionic states moving independently. We use the bosonization procedure with a finite cut-off and obtain a dynamical axion-like field out of the chiral fermionic modes. Then we use relativistic hydrodynamics for macroscopic description of the effective theory obtained after the bosonization. Finally, solving the hydrodynamic equations in gradient expansion, we find that in the presence of external electromagnetic fields the motion of the ''superfluid'' component gives rise to the chiral magnetic, chiral electric and dipole wave effects. Latter two effects are specific for a two-component fluid, which provides us with crucial experimental tests of the model. By considering probe quarks one can show that the fermionic spectrum at the intermediate temperatures (T{sub c}
Chiral density wave in nuclear matter
International Nuclear Information System (INIS)
Inspired by recent work on inhomogeneous chiral condensation in cold, dense quark matter within models featuring quark degrees of freedom, we investigate the chiral density-wave solution in nuclear matter at zero temperature and nonvanishing baryon number density in the framework of the so-called extended linear sigma model (eLSM). The eLSM is an effective model for the strong interaction based on the global chiral symmetry of quantum chromodynamics (QCD). It contains scalar, pseudoscalar, vector, and axial-vector mesons as well as baryons. In the latter sector, the nucleon and its chiral partner are introduced as parity doublets in the mirror assignment. The eLSM simultaneously provides a good description of hadrons in vacuum as well as nuclear matter ground-state properties. We find that an inhomogeneous phase in the form of a chiral density wave is realized, but only for densities larger than 2.4ρ0, where ρ0 is the nuclear matter ground-state density
Introduction to lattice gaugefixing and effective quark and gluon masses
International Nuclear Information System (INIS)
We report on the status of quark and gluon propagators in quenched, gaugefixed lattice QCD. In Landau gauge we find that the effective quark mass in the chiral limit is Mq ∼ 350(40)MeV. Quark and gluon propagators, the slope of the quark dispersion relation, and effective masses all appear to depend on gauge. A link-chain picture of lattice gaugefixing in the color N → ∞ and strong coupling limit, where the system becomes almost solvable, supports the gauge variance of these numerical results
Heavy Quark Solitons in the Nambu--Jona-Lasinio Model
Gamberg, L.(Department of Physics, Penn State University-Berks, Reading, PA, 19610, U.S.A.); Weigel, H.(Physics Department, Stellenbosch University, Matieland 7602, South Africa); Z{ü}ckert, U.; Reinhardt, H.
1995-01-01
The Nambu--Jona-Lasinio model (NJL) is extended to incorporate heavy quark spin-symmetry. In this model baryons containing one heavy quark are analyzed as bound-states of light baryons, represented as chiral solitons, and mesons containing one heavy quark. From related studies in Skyrme type models, the ground-state heavy baryon is known to arise for the heavy meson in a P--wave configuration. In the limit of an infinitely large quark mass the heavy meson wave-function is sharply peaked at th...
The axial charge of the nucleon: lattice results compared with chiral perturbation theory
International Nuclear Information System (INIS)
We present recent Monte Carlo data for the axial charge of the nucleon obtained by the QCDSF-UKQCD collaboration for Nf=2 dynamical quarks. A comparison with chiral perturbation theory in finite and infinite volume is attempted
Going chiral: overlap versus twisted mass fermions
International Nuclear Information System (INIS)
We compare the behavior of overlap fermions, which are chirally invariant, and of Wilson twisted mass fermions at full twist in the approach to the chiral limit. Our quenched simulations reveal that with both formulations of lattice fermions pion masses of O (250 MeV) can be reached in practical applications. Our comparison is done at a fixed value of the lattice spacing a ≅ 0.123 fm. A number of quantities are measured such as hadron masses, pseudoscalar decay constants and quark masses obtained from Ward identities. We also determine the axial vector renormalization constants in the case of overlap fermions. (author)
Going chiral: overlap versus twisted mass fermions
Energy Technology Data Exchange (ETDEWEB)
Bietenholz, Wolfgang [Institut fuer Physik, Humboldt Universitaet zu Berlin, Newtonstr. 15, D-12489 Berlin (Germany); Capitani, Stefano [Institut fuer Physik/Theoretische Physik, Universitaet Graz, A-8010 Graz (Austria); Chiarappa, Thomas [NIC/DESY Zeuthen, Platanenallee 6, D-15738 Zeuthen (Germany)] [and others
2004-12-01
We compare the behavior of overlap fermions, which are chirally invariant, and of Wilson twisted mass fermions at full twist in the approach to the chiral limit. Our quenched simulations reveal that with both formulations of lattice fermions pion masses of O (250 MeV) can be reached in practical applications. Our comparison is done at a fixed value of the lattice spacing a {approx_equal} 0.123 fm. A number of quantities are measured such as hadron masses, pseudoscalar decay constants and quark masses obtained from Ward identities. We also determine the axial vector renormalization constants in the case of overlap fermions. (author)
Pentaquarks in chiral color dielectric model
Indian Academy of Sciences (India)
S C Pathak
2006-04-01
Recent experiments indicate that a narrow baryonic state having strangeness +1 and mass of about 1540 MeV may be existing. Such a state was predicted in chiral model by Diakonov et al. In this work I compute the mass and width of this state in chiral color dielectric model. I show that the computed width is about 30 MeV. I find that the mass of the state can be fitted to the experimentally observed mass by invoking a color neutral vector field and its interaction with the quarks.
Charged pion condensation in the chiral limit
International Nuclear Information System (INIS)
We examine, in the chiral limit where the up and down quark masses are vanishingly small, the stability of the pure neutron ground state to small fluctuations due to charge and baryon number conserving strong interactions. It is shown that the ground state energy density as a function of pion field expectation value is determined by Weinberg's baryon two-body potential and by a calculable neutron-proton mass difference in the medium. This provides some insight into the competing physical effects that play a role in determining whether a charged pion condensate forms in dense nuclear matter. We find that in the chiral limit these effects suppress charged pion condensation. (orig.)
Chiral Symmetry Breaking from Center Vortices
Höllwieser, Roman; Schweigler, Thomas; Heller, Urs M
2014-01-01
We analyze the creation of near-zero modes from would-be zero modes of various topological charge contributions from classical center vortices in SU(2) lattice gauge theory. We show that colorful spherical vortex and instanton configurations have very similar Dirac eigenmodes and also vortex intersections are able to give rise to a finite density of near-zero modes, leading to chiral symmetry breaking via the Banks-Casher formula. We discuss the influence of the magnetic vortex fluxes on quarks and how center vortices may break chiral symmetry.
Heavy-tailed chiral random matrix theory
Kanazawa, Takuya
2016-01-01
We study an unconventional chiral random matrix model with a heavy-tailed probabilistic weight. The model is shown to exhibit chiral symmetry breaking with no bilinear condensate, in analogy to the Stern phase of QCD. We solve the model analytically and obtain the microscopic spectral density and the smallest eigenvalue distribution for an arbitrary number of flavors and arbitrary quark masses. Exotic behaviors such as non-decoupling of heavy flavors and a power-law tail of the smallest eigenvalue distribution are illustrated.
Dvornikov, Maxim
2016-01-01
We study the generation of strong large scale magnetic fields in dense quark matter. The magnetic field growth is owing to the magnetic field instability driven by the electroweak interaction of quarks. We discuss the situation when the chiral symmetry is unbroken in the degenerate quark matter. In this case we predict the amplification of the seed magnetic field $10^{12}\\,\\text{G}$ to the strengths $(10^{14}-10^{15})\\,\\text{G}$. In our analysis we use the typical parameters of the quark matter in the core of a hybrid star or in a quark star. We also discuss the application of the obtained results to describe the magnetic fields generation in magnetars.
Low-energy particle physics and chiral extrapolations
Wittig, Hartmut
2012-01-01
In this review I discuss the role of chiral extrapolations for the determination of several phenomenologically relevant quantities, including light quark masses, meson decay constants and the axial charge of the nucleon. In particular, I investigate whether chiral extrapolations are sufficiently controlled in order to rightfully claim the accuracy which is quoted in recent compilations of these quantities. While this is the case for the masses of the light quarks and the ratio fK/fpi of decay constants, small inconsistencies in the chiral and continuum behaviour of individual decay constants fK and fpi, as well as the hadronic radii r0, r1 remain and must be clarified. In the case of the nucleon axial charge, gA, the chiral behaviour is still poorly understood due to the presence of other systematic effects.
Quark Interchange Model of Baryon Interactions.
Maslow, Joel Neal
The strong interactions at low energy are traditionally described by meson field theories treating hadrons as point -like particles. Here a mesonic quark interchange model (QIM) is presented which takes into account the finite size of the baryons and the internal quark structure of hadrons. The model incorporates the basic quark-gluon coupling of quantum chromodynamics (QCD) and the MIT bag model for color confinement. Because the quark-gluon coupling constant is large and we assume that confinement excludes overlap of hadronic quark bags except at high momenta, a non-perturbative method of nuclear interactions is presented. The QIM allows for exchange of quark quantum numbers at the bag boundary between colliding hadrons mediated at short distances by a gluon exchange between two quarks within the hadronic interior. This generates, via a Fierz transformation, an effective space-like t channel exchange of color singlet (qq) states that can be identified with the low lying meson multiplets. Thus, a one boson exchange (OBE) model is obtained that allows for comparison with traditional phenomenological models of nuclear scattering. Inclusion of strange quarks enables calculation of Yn scattering. The NN and YN coupling constants and the nucleon form factors show good agreement with experimental values as do the deuteron low energy data and the NN low energy phase shifts. Thus, the QIM provides a simple model of strong interactions that is chirally invariant, includes confinement and allows for an OBE form of hadronic interaction at low energies and momentum transfers.
Quark interchange model of baryon interactions
International Nuclear Information System (INIS)
The strong interactions at low energy are traditionally described by meson field theories treating hadrons as point-like particles. Here a mesonic quark interchange model (QIM) is presented which takes into account the finite size of the baryons and the internal quark structure of hadrons. The model incorporates the basic quark-gluon coupling of quantum chromodynamics (QCD) and the MIT bag model for color confinement. Because the quark-gluon coupling constant is large and it is assumed that confinement excludes overlap of hadronic quark bags except at high momenta, a non-perturbative method of nuclear interactions is presented. The QIM allows for exchange of quark quantum numbers at the bag boundary between colliding hadrons mediated at short distances by a gluon exchange between two quarks within the hadronic interior. This generates, via a Fierz transformation, an effective space-like t channel exchange of color singlet (q anti-q) states that can be identified with the low lying meson multiplets. Thus, a one boson exchange (OBE) model is obtained that allows for comparison with traditional phenomenological models of nuclear scattering. Inclusion of strange quarks enables calculation of YN scattering. The NN and YN coupling constants and the nucleon form factors show good agreement with experimental values as do the deuteron low energy data and the NN low energy phase shifts. Thus, the QIM provides a simple model of strong interactions that is chirally invariant, includes confinement and allows for an OBE form of hadronic interaction at low energies and momentum transfers
Quark interchange model of baryon interactions
Energy Technology Data Exchange (ETDEWEB)
Maslow, J.N.
1983-01-01
The strong interactions at low energy are traditionally described by meson field theories treating hadrons as point-like particles. Here a mesonic quark interchange model (QIM) is presented which takes into account the finite size of the baryons and the internal quark structure of hadrons. The model incorporates the basic quark-gluon coupling of quantum chromodynamics (QCD) and the MIT bag model for color confinement. Because the quark-gluon coupling constant is large and it is assumed that confinement excludes overlap of hadronic quark bags except at high momenta, a non-perturbative method of nuclear interactions is presented. The QIM allows for exchange of quark quantum numbers at the bag boundary between colliding hadrons mediated at short distances by a gluon exchange between two quarks within the hadronic interior. This generates, via a Fierz transformation, an effective space-like t channel exchange of color singlet (q anti-q) states that can be identified with the low lying meson multiplets. Thus, a one boson exchange (OBE) model is obtained that allows for comparison with traditional phenomenological models of nuclear scattering. Inclusion of strange quarks enables calculation of YN scattering. The NN and YN coupling constants and the nucleon form factors show good agreement with experimental values as do the deuteron low energy data and the NN low energy phase shifts. Thus, the QIM provides a simple model of strong interactions that is chirally invariant, includes confinement and allows for an OBE form of hadronic interaction at low energies and momentum transfers.
Gleiser, Marcelo; Thorarinson, Joel; Walker, Sara Imari
2008-01-01
Most biomolecules occur in mirror, or chiral, images of each other. However, life is homochiral: proteins contain almost exclusively levorotatory (L) amino acids, while only dextrorotatory (R) sugars appear in RNA and DNA. The mechanism behind this fundamental asymmetry of life remains an open problem. Coupling the spatiotemporal evolution of a general autocatalytic polymerization reaction network to external environmental effects, we show through a detailed statistical analysis that high int...
Small quark stars in the chromodielectric model
Malheiro, M; Nuss, L G; Fiolhais, M; Taurines, A R
2001-01-01
The Chromodielectric Model with a quartic potential is used to describe homogeneous strange quark matter, in beta equilibrium, at high densities. Two equations of state (EOS) are obtained for the same set of model parameters: one corresponds to a chiral restored phase with almost massless quarks and no electrons, and the other to a chiral broken phase. Depending on the model parameters, a phase transition between the two phases may occur. With those EOS the structure of compact stars is investigated and two types of stars are obtained: larger ones with radius $R\\sim 10 - 12$ km, a hadron mantle and a mass $M\\sim 1- 2 M_\\odot$, and smaller pure quark stars, in a chiral restored phase, with $R\\sim 5 - 8$ km, $M\\sim M_\\odot$ and a large baryon density at the edge. The phenomenology of the compact object RX J185635-3754, whose best fit for the radius and mass is $R\\sim 6$ km and $M\\sim 0.9 M_\\odot$, lies in the class of small quark stars predicted by the chromodielectric model.
Energy Technology Data Exchange (ETDEWEB)
Zou, Dandan; Cao, Xin [State Key Laboratory of Advanced Electromagnetic Engineering and Technology, Huazhong University of Science and Technology, Wuhan, Hubei 430074 (China); Lu, Xinpei, E-mail: luxinpei@hotmail.com [State Key Laboratory of Advanced Electromagnetic Engineering and Technology, Huazhong University of Science and Technology, Wuhan, Hubei 430074 (China); IFSA Collaborative Innovation Center, Shanghai Jiao Tong University, Shanghai 200240 (China); Ostrikov, Kostya [School of Chemistry, Physics and Mechanical Engineering, Queensland University of Technology, Brisbane, Queensland 4000 (Australia); Comonwealth Scientific and Industrial Research Organization, P.O. Box 218, Sydney, New South Wales 2070 (Australia)
2015-10-15
The interaction of time-varying electromagnetic fields and solid, liquid, and gaseous matter may lead to electrical breakdown phenomena through the excitation of ionization waves or streamers that control the dynamics of localized plasma propagation through the media. The streamers usually propagate along straight lines, either between random points in space or along a certain direction in a guided mode. Here, we report on a new type of plasma discharges with the regular helical propagation pattern driven by a pulsed dc voltage in nitrogen at sub-atmospheric-pressure conditions. The helical guided streamers, named chiral streamers or chi-streamers, are excited without any external magnetic fields, which commonly cause helical plasma motions. We also demonstrate a hybrid propagation mode involving the interchangeable chiral streamers and the straight-line propagating plasmas. High-speed, time-resolved optical imaging reveals that the chiral streamers and the hybrid patterns are made of spatially localized discrete plasma bullets, similar to the straight-line guided streamers. These results may enable effective control of propagation of confined plasmas and electromagnetic energy along pre-determined, potentially deterministic paths, which have important implications for the development of next-generation plasma-based radiation sources, communication devices, and medical treatments.
Zou, Dandan; Cao, Xin; Lu, Xinpei; Ostrikov, Kostya Ken
2015-10-01
The interaction of time-varying electromagnetic fields and solid, liquid, and gaseous matter may lead to electrical breakdown phenomena through the excitation of ionization waves or streamers that control the dynamics of localized plasma propagation through the media. The streamers usually propagate along straight lines, either between random points in space or along a certain direction in a guided mode. Here, we report on a new type of plasma discharges with the regular helical propagation pattern driven by a pulsed dc voltage in nitrogen at sub-atmospheric-pressure conditions. The helical guided streamers, named chiral streamers or chi-streamers, are excited without any external magnetic fields, which commonly cause helical plasma motions. We also demonstrate a hybrid propagation mode involving the interchangeable chiral streamers and the straight-line propagating plasmas. High-speed, time-resolved optical imaging reveals that the chiral streamers and the hybrid patterns are made of spatially localized discrete plasma bullets, similar to the straight-line guided streamers. These results may enable effective control of propagation of confined plasmas and electromagnetic energy along pre-determined, potentially deterministic paths, which have important implications for the development of next-generation plasma-based radiation sources, communication devices, and medical treatments.
Chiral models of low energy QCD
International Nuclear Information System (INIS)
Two processes may be distinguished when a hadron propagates in a dense baryonic medium. The polarization of the medium and the change in the quark structure of the hadron. The polarization of the medium is better described in terms of colorless mesons and nucleons while the intrinsic change of the hadron is better described by quark models. It is shown how to couple the two processes. The scaling of effective Lagrangians, is related to changes in the quark constituent masses, based on the QCD scale anomaly. (author) 62 refs
Need for spontaneous breakdown of chiral symmetry
Energy Technology Data Exchange (ETDEWEB)
Salomone, A.; Schechter, J.; Tudron, T.
1981-07-15
The question of whether the chiral symmetry of the theory of strong interactions (with massless quarks) is required to be spontaneously broken is examined in the framework of a previously discussed effective Lagrangian for quantum chromodynamics. The assumption that physical masses of the theory be finite leads in a very direct way to the necessity of spontaneous breakdown. This result holds for all N/sub F/> or =2, where N/sub F/ is the number of different flavors of light quarks. The atypical cases N/sub F/ = 1,2 are discussed separately.
Quenched Chiral Behavior of Hadrons with Overlap Fermions
International Nuclear Information System (INIS)
We study the quenched chiral behavior of hadrons with the pseudoscalar mass as low as ∼ 280 MeV. We look for quenched chiral logs in the pion mass, determine the renormalized quark mass, and observe quenched artifacts in the a0 and N* propagators. The calculation is done on a quenched lattice of size 204 and a = 0.148(2) fm using overlap fermions and an improved gauge action
Chiral condensate from the twisted mass Dirac operator spectrum
Energy Technology Data Exchange (ETDEWEB)
Cichy, Krzysztof [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC; Poznan Univ. (Poland). Faculty of Physics; Garcia-Ramos, Elena [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC; Humboldt-Universitaet, Berlin (Germany); Jansen, Karl [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC; Cyprus Univ., Nicosia (Cyprus). Dept. of Physics; Collaboration: European Twisted Mass Collaboration
2013-03-15
We present the results of our computation of the chiral condensate with N{sub f}=2 and N{sub f}=2+1+1 flavours of maximally twisted mass fermions. The condensate is determined from the Dirac operator spectrum, applying the spectral projector method proposed by Giusti and Luescher. We use 3 lattice spacings and several quark masses at each lattice spacing to reliably perform the chiral and continuum extrapolations. We study the effect of the dynamical strange and charm quarks by comparing our results for N{sub f}=2 and N{sub f}=2+1+1 dynamical flavours.
Distinguishing Standard Model Extensions using Monotop Chirality at the LHC
Allahverdi, Rouzbeh; Dutta, Bhaskar; Gao, Yu; Kamon, Teruki
2015-01-01
We present two minimal extensions of the standard model that gives rise to baryogensis and include heavy color-triplet scalars interacting with a light Majorana fermion that can be the dark matter (DM) candidate. The electroweak charges of the new scalars govern their couplings to quarks of different chirality, which leads to different collider signals. These models predict monotop events at the LHC and the energy spectrum of decay products of highly polarized top quarks can be used to establish the chiral nature of the interactions involving the heavy scalars and the DM.
QCD with chiral 4-fermion interactions (χQCD)
International Nuclear Information System (INIS)
Lattice QCD with staggered quarks is augmented by the addition of a chiral 4-fermion interaction. The Dirac operator is now non-singular at mq=0, decreasing the computing requirements for light quark simulations by at least an order of magnitude. We present preliminary results from simulations at finite and zero temperatures for mq=0, with and without gauge fields. Chiral QCD enables simulations at physical u and d quark masses with at least an order of magnitude saving in CPU time. It also enables simulations with zero quark masses which is important for determining the equation of state. A renormalization group analysis will be needed to continue to the continuum limit. 7 refs., 2 figs
Soap opera: the sad tale of the quark
International Nuclear Information System (INIS)
The history of quark physics is briefly reviewed, followed by an introduction to quantum chromodynamics, leading terms, and the OZI rule. The basic physics of hadron structure as revealed by experiment is then discussed, followed by the models used to treat it. The two complementary models are the quasinuclear colored quark model and the quark-parton model. Another model for orthogonal physical properties is the bag model. Several applications of the constituent quark model are considered, including hadron masses, spin physics, and multiquark physics. The theoretical basis and phenomenology of the OZI rule forbids processes described by disconnected quark line diagrams
Evidence for chiral logarithms in the baryon spectrum
Walker-Loud, Andre
2011-01-01
Using precise lattice QCD computations of the baryon spectrum, we present the first direct evidence for the presence of contributions to the baryon masses which are non-analytic in the light quark masses; contributions which are often denoted "chiral logarithms". We isolate the poor convergence of SU(3) baryon chiral perturbation theory to the flavor-singlet mass combination. The flavor-octet baryon mass splittings, which are corrected by chiral logarithms at next to leading order in SU(3) chiral perturbation theory, yield baryon-pion axial coupling constants D, F, C and H consistent with QCD values; the first evidence of chiral logarithms in the baryon spectrum. The Gell-Mann--Okubo relation, a flavor-27 baryon mass splitting, which is dominated by chiral corrections from light quark masses, provides further evidence for the presence of non-analytic light quark mass dependence in the baryon spectrum; we simultaneously find the GMO relation to be inconsistent with the first few terms in a taylor expansion in ...
Diffractive dissociation and new quarks
International Nuclear Information System (INIS)
We argue that the chiral limit of QCD can be identified with the strong (diffractive dissociation) coupling limit of reggeon field theory. Critical Pomeron scaling at high energy must then be directly related to an infra-red fixed-point of massless QCD and so requires a large number of flavors. This gives a direct argument that the emergence of diffraction-peak scaling, KNO scaling etc. at anti p-p colliders are evidence of a substantial quark structure still to be discovered
Horn, D.
2015-03-01
The quark model emerged from the Gell-Mann-Ne'eman flavor SU(3) symmetry. Its development, in the context of strong interactions, took place in a heuristic theoretical framework, referred to as the Bootstrap Era. Setting the background for the dominant ideas in strong interaction of the early 1960s, we outline some aspects of the constituent quark model. An independent theoretical development was the emergence of hadron duality in 1967, leading to a realization of the Bootstrap idea by relating hadron resonances (in the s-channel) with Regge pole trajectories (in t- and u-channels). The synthesis of duality with the quark-model has been achieved by duality diagrams, serving as a conceptual framework for discussing many aspects of hadron dynamics toward the end of the 1960s.
Chiral geometry in multiple chiral doublet bands
Zhang, Hao
2015-01-01
The chiral geometry of the multiple chiral doublet bands with identical configuration is discussed for different triaxial deformation parameters $\\gamma$ in the particle rotor model with $\\pi h_{11/2}\\otimes \
Institute of Scientific and Technical Information of China (English)
ZONG Hong-Shi; SUN Wei-Min; PING Jia-Lun; L(U) Xiao-Fu; WANG Fan
2005-01-01
@@ It is shown on general ground that there exist two qualitatively distinct solutions of the Dyson-Schwinger equation for the quark propagator in the case of non-zero current quark mass. One solution corresponds to the "NambuGoldstone" phase and the other one corresponds to the "Wigner" phase in the chiral limit.
Chiral symmetry breakdown and the spectrum of pseudoscalar mesons in quantum chromodynamics
International Nuclear Information System (INIS)
The recently suggested mechanism of the dynamical chiral symmetry breakdown in quantum chromodynamics is extended to the realistic situation when both spontaneous and explicit chiral symmetry breaking take place (current masses of the light quarks are different from zero). The mass relations for pseudoscalar nonet are obtained
Non-uniform chiral phase studied within the Polyakov NJL model
Partyka, Tomasz L.
2010-01-01
We consider how does the introduction of a Polyakov loop affects the spatially inhomogeneous quark condensate. The primary result of our work is that the existence of the spatially non-uniform chiral phase is confirmed within the Polyakov NJL model in a chiral limit. These findings are obtained both in a 3d-cutoff and in a Schwinger (proper time) regularization schemes.
Baryons in QCD and chiral symmetry breaking parameters
International Nuclear Information System (INIS)
We calculate all baryons in the 56 representation using QCD sum rules. All masses are well predicted and require stringent values of the chiral parameters (0vertical strokeanti uuvertical stroke0) = -(230 +- 15 MeV)3 and ν = (anti ss)/(uu) - 1 = -0.19 +- 0.02. The determination of ν is the most precise to date, the strange quark mass and the quark condensate are also accurately fixed. (orig.)
Dynamical twisted mass fermions with light quarks
International Nuclear Information System (INIS)
We present results of dynamical simulations of Nf=2 degenerate Wilson twisted mass quarks at maximal twist in the range of pseudo scalar masses 300 MeVPS 2) cutoff effects, the theory is tuned to maximal twist by requiring the vanishing of the untwisted quark mass. Precise results for the pseudo scalar decay constant and the pseudo scalar mass are confronted with chiral perturbation theory predictions and the low energy constants F, anti l3 and anti l4 are evaluated with small statistical errors. (orig.)
Scalar resonances as two-quark states
International Nuclear Information System (INIS)
On the base of the theory with U(3)xU(3) symmetric chiral Lagrangian the properties of the two-quark scalar mesons are considered. It is shown, that the scalar resonances delta (980) and K(1240) may be treated as the p-wave states of anti qq system. The properties of the isovector and strange scalar mesons, obtained as a propetrties of the two-quark states, turn out to be very close to the properties of the isovector scalar resonance delta (980) and strange resonance K(1240)
Examining a possible cascade effect in chiral symmetry breaking
Fariborz, Amir H
2016-01-01
We examine a toy model and a cascade effect for confinement and chiral symmetry breaking which consists in several phase transitions corresponding to the formation of bound states and chiral condensates with different number of fermions for a strong group. We analyze two examples: regular QCD where we calculate the "four quark" vacuum condensate and a preon composite model based on QCD at higher scales. In this context we also determine the number of flavors at which the second chiral and confinement phase transitions occur and discuss the consequences.
Mesons in Nuclei and Partial Restoration of Chiral Symmetry
Jido, Daisuke
2016-01-01
Recent topics on mesons in nuclei are discussed by especially emphasizing the role of the partial restoration of chiral symmetry in the nuclear medium. The spontaneously broken chiral symmetry in vacuum is considered to be incompletely restored in finite nuclear density systems with moderate reduction of the magnitude of the quark condensate. On the partial restoration of chiral symmetry, the wave function renormalization is important to be taken into account for the Nambu-Goldstone bosons. We also discuss the possible change of the meson properties in the nuclear medium and meson-nucleus systems for the $\\bar K$, $\\eta$, $K^{+}$ and $\\eta^{\\prime}$ mesons.
No-Drag Frame for Anomalous Chiral Fluid
Stephanov, Mikhail A.; Yee, Ho-Ung
2016-03-01
We show that for an anomalous fluid carrying dissipationless chiral magnetic and/or vortical currents there is a frame in which a stationary obstacle experiences no drag, but energy and charge currents do not vanish, resembling superfluidity. However, unlike ordinary superfluid flow, the anomalous chiral currents can transport entropy in this frame. We show that the second law of thermodynamics completely determines the amounts of these anomalous nondissipative currents in the "no-drag frame" as polynomials in temperature and chemical potential with known anomaly coefficients. These general results are illustrated and confirmed by a calculation in the chiral kinetic theory and in the quark-gluon plasma at high temperature.
The no-drag frame for anomalous chiral fluid
Stephanov, Mikhail A
2015-01-01
We show that for an anomalous fluid carrying dissipationless chiral magnetic and/or vortical currents there is a frame in which a stationary obstacle experiences no drag, but energy and charge currents do not vanish, resembling superfluidity. However, unlike ordinary superfluid flow, the anomalous chiral currents do transport entropy in this frame. We show that the second law of thermodynamics completely determines the amounts of these anomalous non-dissipative currents in the "no-drag frame" as polynomials in temperature and chemical potential with known anomaly coefficients. These general results are illustrated and confirmed by a calculation in the chiral kinetic theory and quark-gluon plasma at high temperature.
Hot Quark Matter with an Axial Chemical Potential
Gatto, Raoul
2011-01-01
We analyze the phase diagram of hot quark matter in presence of an axial chemical potential, $\\mu_5$. The latter is introduced to mimic the chirality transitions induced, in hot Quantum Chromodynamics, by the strong sphaleron configurations. In particular, we study the curvature of the critical line at small $\\mu_5$, the effects of a finite quark mass and of a vector interaction. Moreover, we build the mixed phase at the first order phase transition line, and draw the phase diagram in the chiral density and temperature plane. We finally compute the full topological susceptibility in presence of a background of topological charge.
Chiral symmetry breaking in brane models
International Nuclear Information System (INIS)
We discuss the chiral symmetry breaking in general intersecting Dq/Dp brane models consisting of Nc Dq-branes and a single Dp-brane with an s-dimensional intersection. There exists a QCD-like theory localized at the intersection and the Dq/Dp model gives a holographic description of it. The rotational symmetry of directions transverse to both of the Dq and Dp-branes can be identified with a chiral symmetry, which is non-Abelian for certain cases. The asymptotic distance between the Dq-branes and the Dp-brane corresponds to a quark mass. By studying the probe Dp-brane dynamics in a Dq-brane background in the near horizon and large Nc limit we find that the chiral symmetry is spontaneously broken and there appear (pseudo-)Nambu-Goldstone bosons. We also discuss the models at finite temperature
International Nuclear Information System (INIS)
We discuss the results accumulated during the last five years in heavy quark physics and try to draw a simple general picture of the present situation. The survey is based on a unified point of view resulting from quantum chromodynamics. (orig.)
Harigaya, Keisuke
2016-01-01
An interesting possibility for dark matter is a scalar particle of mass of order 10 MeV-1 GeV, interacting with a U(1) gauge boson (dark photon) which mixes with the photon. We present a simple and natural model realizing this possibility. The dark matter arises as a composite pseudo Nambu-Goldstone boson (dark pion) in a non-Abelian gauge sector, which also gives a mass to the dark photon. For a fixed non-Abelian gauge group, SU(N), and a U(1) charge of the constituent dark quarks, the model has only three free parameters: the dynamical scale of the non-Abelian gauge theory, the gauge coupling of the dark photon, and the mixing parameter between the dark and standard model photons. In particular, the gauge symmetry of the model does not allow any mass term for the dark quarks, and stability of the dark pion is understood as a result of an accidental global symmetry. The model has a significant parameter space in which thermal relic dark pions comprise all of the dark matter, consistently with all experimenta...
Inhomogeneous chiral symmetry breaking in dense neutron-star matter
Buballa, Michael
2015-01-01
An increasing number of model results suggests that chiral symmetry is broken inhomogeneously in a certain window at intermediate densities in the QCD phase diagram. This could have significant effects on the properties of compact stars, possibly leading to new astrophysical signatures. In this contribution we discuss this idea by reviewing recent results on inhomogeneous chiral symmetry breaking under an astrophysics-oriented perspective. After introducing two commonly studied spatial modulations of the chiral condensate, the chiral density wave and the real kink crystal, we focus on their properties and their effect on the equation of state of quark matter. We also describe how these crystalline phases are affected by different elements which are required for a realistic description of a compact star, such as charge neutrality, the presence of magnetic fields, vector interactions and the interplay with color-superconductivity. Finally, we discuss possible signatures of inhomogeneous chiral symmetry breaking...
On chiral symmetry breaking, topology and confinement
Energy Technology Data Exchange (ETDEWEB)
Shuryak, Edward
2014-08-15
We start with the relation between the chiral symmetry breaking and gauge field topology. New lattice results further enhance the notion of Zero Mode Zone, a very narrow strip of states with quasizero Dirac eigenvalues. Then we move to the issue of “origin of mass” and Brown–Rho scaling: a number of empirical facts contradicts to the idea that masses of quarks and such hadrons as ρ,N decrease near T{sub c}. We argue that while at T=0 the main contribution to the effective quark mass is chirally odd m{sub χ/}, near T{sub c} it rotates to chirally-even component m{sub χ}, because “infinite clusters” of topological solitons gets split into finite ones. Recent progress in understanding of topology require introduction of nonzero holonomy 〈A{sub 0}〉≠0, which splits instantons into N{sub c} (anti)selfdual “instanton–dyons”. Qualitative progress, as well as first numerical studies of the dyon ensemble are reported. New connections between chiral symmetry breaking and confinement are recently understood, since instanton–dyons generate holonomy potential with a minimum at confining value, if the ensemble is dense enough.
On the quark-mass dependence of baryon ground-state masses
Energy Technology Data Exchange (ETDEWEB)
Semke, Alexander
2010-02-17
Baryon masses of the flavour SU(3) octet and decuplet baryons are calculated in the framework of the Chiral Perturbations Theory - the effective field theory of the strong interaction. The chiral extrapolation to the higher meson (quark) masses is carried out. The comparison with the recent results on the baryon masses from lattice calculations are presented. (orig.)
On the quark-mass dependence of baryon ground-state masses
International Nuclear Information System (INIS)
Baryon masses of the flavour SU(3) octet and decuplet baryons are calculated in the framework of the Chiral Perturbations Theory - the effective field theory of the strong interaction. The chiral extrapolation to the higher meson (quark) masses is carried out. The comparison with the recent results on the baryon masses from lattice calculations are presented. (orig.)
Chiral matrix model of the semi-QGP in QCD
Pisarski, Robert D.; Skokov, Vladimir V.
2016-08-01
Previously, a matrix model of the region near the transition temperature, in the "semi"quark gluon plasma, was developed for the theory of S U (3 ) gluons without quarks. In this paper we develop a chiral matrix model applicable to QCD by including dynamical quarks with 2 +1 flavors. This requires adding a nonet of scalar fields, with both parities, and coupling these to quarks through a Yukawa coupling, y . Treating the scalar fields in mean field approximation, the effective Lagrangian is computed by integrating out quarks to one loop order. As is standard, the potential for the scalar fields is chosen to be symmetric under the flavor symmetry of S U (3 )L×S U (3 )R×Z (3 )A, except for a term linear in the current quark mass, mqk. In addition, at a nonzero temperature T it is necessary to add a new term, ˜mqkT2. The parameters of the gluon part of the matrix model are identical to those for the pure glue theory without quarks. The parameters in the chiral matrix model are fixed by the values, at zero temperature, of the pion decay constant and the masses of the pions, kaons, η , and η'. The temperature for the chiral crossover at Tχ=155 MeV is determined by adjusting the Yukawa coupling y . We find reasonable agreement with the results of numerical simulations on the lattice for the pressure and related quantities. In the chiral limit, besides the divergence in the chiral susceptibility there is also a milder divergence in the susceptibility between the Polyakov loop and the chiral order parameter, with critical exponent β -1 . We compute derivatives with respect to a quark chemical potential to determine the susceptibilities for baryon number, the χ2 n. Especially sensitive tests are provided by χ4-χ2 and by χ6, which changes in sign about Tχ. The behavior of the susceptibilities in the chiral matrix model strongly suggests that as the temperature increases from Tχ, that the transition to deconfinement is significantly quicker than indicated by the
Structure of the vacuum in the color dielectric model: confinement and chiral symmetry
International Nuclear Information System (INIS)
Two of the most important properties of Quantum Chromodynamic (QCD), spontaneous symmetry breaking of the vacuum and quark confinement at low energy, are first presented. Some important effective models for hadronic physics are then described. Putting QCD on the lattice and using the block-spin method, the color-dielectric model effective Lagrangian is obtained. The structure of the vacuum and the behaviour of uniform quark matter at high intensity are investigated in this model. Its original formulation is extended to handle chiral symmetry (by use of sigma model) and to include negative energy orbitals. At high baryonic density, the model describes the two phase transitions which are expected in QCD: deconfinement of quarks and chiral symmetry restoration. Finally, a heavy meson composed by a charmed quark anti-quark pair, is constructed, and the valence quarks confinement and the vacuum structure around them are studied
NLO QCD corrections to dijet production via quark contact interactions
Gao, Jun; Li, Chong Sheng; Yuan, C. -P.
2012-01-01
We present the exact next-to-leading order (NLO) QCD corrections to dijet production at the LHC via quark contact interactions, with different color and chiral structures induced from new physics. Following the recent analysis of quark compositeness search at the LHC, we find that the NLO QCD corrections can lower the dijet cross sections by several tens percent, depending on the theory parameters and the selected kinematic regions, and reduce the dependence of the cross sections on factoriza...
Chiral symmetry and chiral-symmetry breaking
International Nuclear Information System (INIS)
These lectures concern the dynamics of fermions in strong interaction with gauge fields. Systems of fermions coupled by gauge forces have a very rich structure of global symmetries, which are called chiral symmetries. These lectures will focus on the realization of chiral symmetries and the causes and consequences of thier spontaneous breaking. A brief introduction to the basic formalism and concepts of chiral symmetry breaking is given, then some explicit calculations of chiral symmetry breaking in gauge theories are given, treating first parity-invariant and then chiral models. These calculations are meant to be illustrative rather than accurate; they make use of unjustified mathematical approximations which serve to make the physics more clear. Some formal constraints on chiral symmetry breaking are discussed which illuminate and extend the results of our more explicit analysis. Finally, a brief review of the phenomenological theory of chiral symmetry breaking is presented, and some applications of this theory to problems in weak-interaction physics are discussed
NJL model approach to diquarks and baryons in quark matter
Blaschke, D; Zablocki, D
2015-01-01
We describe baryons as quark-diquark bound states at finite temperature and density within the NJL model for chiral symmetry breaking and restoration in quark matter. Based on a generalized Beth-Uhlenbeck approach to mesons and diquarks we present in a first step the thermodynamics of quark-diquark matter which includes the Mott dissociation of diquarks at finite temperature. In a second step we solve the Bethe-Salpeter equation for the baryon as a quark-diquark bound state in quark-diquark matter. We obtain a stable, bound baryon even beyond the Mott temperature for diquark dissociation since the phase space occupation effect (Pauli blocking for quarks and Bose enhancement for diquarks) in the Bethe-Salpeter kernel for the nucleon approximately cancel so that the nucleon mass follows the in-medium behaviour of the quark and diquark masses towards chiral restoration. In this situation the baryon is obtained as a "borromean" three-quark state in medium because the two-particle state (diquark) is unbound while ...
Stiele, Rainer; Schaffner-Bielich, Juergen
2016-01-01
Unquenching of the Polyakov-loop potential showed to be an important improvement for the description of the phase structure and thermodynamics of strongly-interacting matter at zero quark chemical potentials with Polyakov-loop extended chiral models. This work constitutes the first application of the quark backreaction on the Polyakov-loop potential at nonzero density. The observation is that it links the chiral and deconfinement phase transition also at small temperatures and large quark che...
Contribution of Quark Structure Term in Nucleon Electric and Magnetic Form Factors
Institute of Scientific and Technical Information of China (English)
WANG Hong-Min; ZHANG Ben-Ai
2004-01-01
The constituent quarks in the nucleon have always been considered as a point-like particle in the relativistic constituent quark model. However its calculation results of GnE agree poorly with the new experimental data. The electromagnetic structure of light front constituent quarks is considered in this paper. We find that the calculation results have good agreement with the new experimental data of GnE after considering the contribution of the quark structure term. This treatment seems to be able to improve the fit to experimental data of Gep/GMp, /Q2F2p/kpF1p,and Gen/GMn as well.
Nuclear phenomena derived from quark-gluon strings
DEFF Research Database (Denmark)
Bohr, Henrik; Providencia, Constanca; Providencia, Joao da
2005-01-01
chirality provided that the chiral fields are identified with the two-particle strings, which are natural in a QCD framework. Moreover, the model is able to reconcile qualitatively such aspects of hadronic physics as saturation density and binding energy of nuclear matter, surface density of finite nuclei......, for the occurrence of the phases of nuclear matter. The model exhibits a quark deconfinement transition and chiral restoration, which are ingredients of QCD and give qualitatively correct numerics. The effective model is shown to be isomorphic to the Nambu-Jona-Lasinio model and exhibits the correct...
Non-perturbative studies of QCD at small quark masses
Energy Technology Data Exchange (ETDEWEB)
Wennekers, J.
2006-07-15
We investigate the quenched approximation of lattice QCD with numerical simulations of Ginsparg-Wilson fermions, which are a fermion discretisation with exact chiral symmetry. We compute the renormalisation constant of the scalar density, which allows to extrapolate the chiral condensate to the continuum limit. Furthermore we match lattice results of matrix elements describing hadronic kaon decays to Chiral Perturbation Theory in finite volume and at almost vanishing quark mass. The resulting low-energy constants in the considered SU(4)-flavour symmetric case indicate a substantial contribution of low scale QCD effects to the {delta}I = 1/2 rule. (Orig.)
Non-perturbative studies of QCD at small quark masses
International Nuclear Information System (INIS)
We investigate the quenched approximation of lattice QCD with numerical simulations of Ginsparg-Wilson fermions, which are a fermion discretisation with exact chiral symmetry. We compute the renormalisation constant of the scalar density, which allows to extrapolate the chiral condensate to the continuum limit. Furthermore we match lattice results of matrix elements describing hadronic kaon decays to Chiral Perturbation Theory in finite volume and at almost vanishing quark mass. The resulting low-energy constants in the considered SU(4)-flavour symmetric case indicate a substantial contribution of low scale QCD effects to the ΔI = 1/2 rule. (Orig.)
Hadron and Quark Form Factors in the Relativistic Harmonic Oscillator Model
Burov, V. V.; De Pace, A.; Dorkin, S. M.; P. Saracco(INFN, Sezione di Genova)
1993-01-01
Nucleon, pion and quark form factors are studied within the relativistic harmonic oscillator model including the quark spin. It is shown that the nucleon charge, magnetic and axial form factors and the pion charge form factor can be explained with one oscillator parameter if one accounts for the scaling rule and the size of the constituent quarks.
Chiral-symmetry breaking and pion structure in the Covariant Spectator Theory
Biernat, Elmar P; Gross, Franz; Stadler, Alfred; Ribeiro, Emílio
2016-01-01
We introduce a covariant approach in Minkowski space for the description of quarks and mesons that exhibits both chiral-symmetry breaking and confinement. In a simple model for the interquark interaction the quark mass function is obtained and used in the calculation of the pion form factor. We study the effects of the mass function and of the different quark pole contributions on the pion form factor.
Hadronic Lorentz Violation in Chiral Perturbation Theory
Kamand, Rasha; Schindler, Matthias R
2016-01-01
Any possible Lorentz violation in the hadron sector must be tied to Lorentz violation at the underlying quark level. The relationships between the theories at these two levels are studied using chiral perturbation theory. Starting from a two-flavor quark theory that includes dimension-four Lorentz-violation operators, the effective Lagrangians are derived for both pions and nucleons, with novel terms appearing in both sectors. Since the Lorentz violation coefficients for nucleons and pions are all related to a single set of underlying quark coefficients, it is possible to place approximate bounds on pion Lorentz violation using only proton and neutron observations. The resulting bounds on four pion parameters are at the $10^{-23}$ level, representing improvements of ten orders of magnitude.
Energy Technology Data Exchange (ETDEWEB)
Plum, Eric, E-mail: erp@orc.soton.ac.uk [Optoelectronics Research Centre and Centre for Photonic Metamaterials, University of Southampton, Highfield, Southampton SO17 1BJ (United Kingdom); Zheludev, Nikolay I., E-mail: niz@orc.soton.ac.uk [Optoelectronics Research Centre and Centre for Photonic Metamaterials, University of Southampton, Highfield, Southampton SO17 1BJ (United Kingdom); The Photonics Institute and Centre for Disruptive Photonic Technologies, Nanyang Technological University, Singapore 637378 (Singapore)
2015-06-01
Mirrors are used in telescopes, microscopes, photo cameras, lasers, satellite dishes, and everywhere else, where redirection of electromagnetic radiation is required making them arguably the most important optical component. While conventional isotropic mirrors will reflect linear polarizations without change, the handedness of circularly polarized waves is reversed upon reflection. Here, we demonstrate a type of mirror reflecting one circular polarization without changing its handedness, while absorbing the other. The polarization-preserving mirror consists of a planar metasurface with a subwavelength pattern that cannot be superimposed with its mirror image without being lifted out of its plane, and a conventional mirror spaced by a fraction of the wavelength from the metasurface. Such mirrors enable circularly polarized lasers and Fabry-Pérot cavities with enhanced tunability, gyroscopic applications, polarization-sensitive detectors of electromagnetic waves, and can be used to enhance spectroscopies of chiral media.
Amsler, C.; DeGrand, T.; Krusche, B.
2008-01-01
This biennial Review summarizes much of particle physics. Using data from previous editions, plus 2778 new measurements from 645 papers, we list, evaluate, and average measured properties of gauge bosons, leptons, quarks, mesons, and baryons. We also summarize searches for hypothetical particles such as Higgs bosons, heavy neutrinos, and supersymmetric particles. All the particle properties and search limits are listed in Summary Tables. We also give numerous tables, figures, formulae, and re...
Chiral and deconfinement phase transition in the Hamiltonian approach to QCD in Coulomb gauge
Reinhardt, H
2016-01-01
The chiral and deconfinement phase transitions are investigated within the variational Hamiltonian approach to QCD in Coulomb gauge. The temperature $\\beta^{-1}$ is introduced by compactifying a spatial dimension. Thereby the whole temperature dependence is encoded in the vacuum state on the spatial manifold $\\mathbb{R}^2 \\times S^1(\\beta)$. The chiral quark condensate and the dual quark condensate (dressed Polyakov loop) are calculated as function of the temperature. From their inflection points the pseudo-critical temperatures for the chiral and deconfinement crossover transitions are determined. Using the zero-temperature quark and gluon propagators obtained within the variational approach as input, we find 226 MeV and 262 MeV, respectively, for the chiral and deconfinement transition.
Hyun, Chang Ho; Lee, Hee-Jung
2016-01-01
We investigate the parity-violating pion-nucleon-nucleon coupling constant $h^1_{\\pi NN}$, based on the chiral quark-soliton model. We employ an effective weak Hamiltonian that takes into account the next-to-leading order corrections from QCD to the weak interactions at the quark level. Using the gradient expansion, we derive the leading-order effective weak chiral Lagrangian with the low-energy constants determined. The effective weak chiral Lagrangian is incorporated in the chiral quark-soliton model to calculate the parity-violating $\\pi NN$ constant $h^1_{\\pi NN}$. We obtain a value of about $10^{-7}$ at the leading order. The corrections from the next-to-leading order reduce the leading order result by about 20~\\%.
Chiral Lagrangians at finite temperature and the Polyakov Loop
Megias, E.; Arriola, E. Ruiz; Salcedo, L. L.
2004-01-01
Heat kernel expansions at finite temperature of massless QCD and chiral quark models generate effective actions relevant for both low and high temperature QCD. The key relevance of the Polyakov Loop to maintain the large and non-perturbative gauge invariance at finite temperature is stressed.
International Nuclear Information System (INIS)
An approximate model is proposed for a system of three Schroedinger particles of equal masses, interacting mutually through a universal two-body potential. They are assumed to form during their motion a (generally) varying equilateral triangle corresponding to Lagrange's exact triangle solution of the classical three-body problem. The resulting wave equation is formally a two-body Schroedinger equation (in the centre-of-mass frame). This is applied to three constituent quarks in the nucleon. The present model, called ''Lagrange triangle of Schroedinger particles'', may be considered as a non-relativistic approximation to the much more complicated ''Lagrange triangle of Dirac particles'' constructed by the author a decade ago. (author)
Chiral Magnetic Effect in Hydrodynamic Approximation
Zakharov, Valentin I
2012-01-01
We review derivations of the chiral magnetic effect (ChME) in hydrodynamic approximation. The reader is assumed to be familiar with the basics of the effect. The main challenge now is to account for the strong interactions between the constituents of the fluid. The main result is that the ChME is not renormalized: in the hydrodynamic approximation it remains the same as for non-interacting chiral fermions moving in an external magnetic field. The key ingredients in the proof are general laws of thermodynamics and the Adler-Bardeen theorem for the chiral anomaly in external electromagnetic fields. The chiral magnetic effect in hydrodynamics represents a macroscopic manifestation of a quantum phenomenon (chiral anomaly). Moreover, one can argue that the current induced by the magnetic field is dissipation free and talk about a kind of "chiral superconductivity". More precise description is a ballistic transport along magnetic field taking place in equilibrium and in absence of a driving force. The basic limitat...
Constituent models and large transverse momentum reactions
International Nuclear Information System (INIS)
The discussion of constituent models and large transverse momentum reactions includes the structure of hard scattering models, dimensional counting rules for large transverse momentum reactions, dimensional counting and exclusive processes, the deuteron form factor, applications to inclusive reactions, predictions for meson and photon beams, the charge-cubed test for the e/sup +-/p → e/sup +-/γX asymmetry, the quasi-elastic peak in inclusive hadronic reactions, correlations, and the multiplicity bump at large transverse momentum. Also covered are the partition method for bound state calculations, proofs of dimensional counting, minimal neutralization and quark--quark scattering, the development of the constituent interchange model, and the A dependence of high transverse momentum reactions
Chiral symmetry aspects in supersymmetric confining gauge theories
International Nuclear Information System (INIS)
We provide a detailed analysis of the interplay between chiral symmetry and supersymmetry within the context of supersymmetric confining gauge theories. We describe a general method leading to exact results on quark mass dependences of physical quantities such as bound-state masses, bilinear condensates,... We also establish the commutation relations satisfied by the supersymmetric and chiral charges in presence of the soft breaking due to quark masses. We show that, if the chiral limit is unique, the global SUsub(L)(Nsub(f)) x SUsub(R)(Nsub(f)) symmetry is not spontaneously broken. If this limit is not unique, a spontaneous breakdown of the axial symmetry is allowed, but only at the cost of a simultaneous breakdown of the vector symmetry
Quark hadron matter in a unified approach
International Nuclear Information System (INIS)
We present an effective model for the QCD EoS, taking into account chiral symmetry restoration as well as the deconfinement phase transition. For the hadronic part we apply a SUf(3) parity doublet model with quarks introduced in anology to the PNJL model. The correct asymptotic degrees of freedom at the high and low temperature limits are included (quarks hadrons). As expected from lattice calculations, the model shows a rapid crossover for both order parameters at μB=0. We compare thermodynamic properties of the model at μB=0 which are in qualitative agreement with lattice data, while apparent quantitative differences can be attributed to hadronic contributions. Our model reproduces a first-order liquid gas phase transition as expected, and exhibits another first order chiral phase transition at high densities terminated by a critical endpoint. The deconfinement transition appears as a very wide crossover in which heavily medium modified hadrons coexist with free quarks. Furthermore,the full baryonic resonance spectrum is implemented and we study the impact of a varying vector coupling strength on the phase diagram, i.e. the location of the phase transition and the existence of a critical point. We present quark number susceptibilities and compare them to lattice results.
Quark hadron matter in a unified approach
Energy Technology Data Exchange (ETDEWEB)
Rau, Philip; Steinheimer, Jan [Institut fuer Theoretische Physik, Goethe-Universitaet, Frankfurt (Germany); Schramm, Stefan [Institut fuer Theoretische Physik, Goethe-Universitaet, Frankfurt (Germany); Frankfurt Institute for Advanced Studies (FIAS), Frankfurt (Germany); Stoecker, Horst [Institut fuer Theoretische Physik, Goethe-Universitaet, Frankfurt (Germany); Frankfurt Institute for Advanced Studies (FIAS), Frankfurt (Germany); GSI Helmholtzzentrum fuer Schwerionenforschung, Darmstadt (Germany)
2011-07-01
We present an effective model for the QCD EoS, taking into account chiral symmetry restoration as well as the deconfinement phase transition. For the hadronic part we apply a SU{sub f}(3) parity doublet model with quarks introduced in anology to the PNJL model. The correct asymptotic degrees of freedom at the high and low temperature limits are included (quarks <-> hadrons). As expected from lattice calculations, the model shows a rapid crossover for both order parameters at {mu}{sub B}=0. We compare thermodynamic properties of the model at {mu}{sub B}=0 which are in qualitative agreement with lattice data, while apparent quantitative differences can be attributed to hadronic contributions. Our model reproduces a first-order liquid gas phase transition as expected, and exhibits another first order chiral phase transition at high densities terminated by a critical endpoint. The deconfinement transition appears as a very wide crossover in which heavily medium modified hadrons coexist with free quarks. Furthermore,the full baryonic resonance spectrum is implemented and we study the impact of a varying vector coupling strength on the phase diagram, i.e. the location of the phase transition and the existence of a critical point. We present quark number susceptibilities and compare them to lattice results.
Eser, Jürgen; Rischke, Dirk H
2015-01-01
The transition in quantum chromodynamics (QCD) from hadronic matter to the quark-gluon plasma (QGP) at high temperatures and/or net-baryon densities is associated with the restoration of chiral symmetry and can be investigated in the laboratory via heavy-ion collisions. We study this chiral transition within the functional renormalization group (FRG) approach applied to the two-flavor version of the extended Linear Sigma Model (eLSM). The eLSM is an effective model for the strong interaction and features besides scalar and pseudoscalar degrees of freedom also vector and axial- vector mesons. We discuss the impact of the quark masses and the axial anomaly on the order of the chiral transition. We also confirm the degeneracy of the masses of chiral partners above the transition temperature. We find that the mass of the $a_1$ meson ($\\rho$ meson) decreases (increases) towards the chiral transition.
Eser, Jürgen; Grahl, Mara; Rischke, Dirk H.
2015-11-01
The transition in quantum chromodynamics from hadronic matter to the quark-gluon plasma at high temperatures and/or net-baryon densities is associated with the restoration of chiral symmetry and can be investigated in the laboratory via heavy-ion collisions. We study this chiral transition within the functional renormalization group approach applied to the two-flavor version of the extended linear sigma model (eLSM). The eLSM is an effective model for the strong interaction and features besides scalar and pseudoscalar degrees of freedom also vector and axial-vector mesons. We discuss the impact of the quark masses and the axial anomaly on the order of the chiral transition. We also confirm the degeneracy of the masses of chiral partners above the transition temperature. We find that the mass of the a1 meson (ρ meson) decreases (increases) towards the chiral transition.
pi-pi and pi-K scatterings in three-flavour resummed chiral perturbation theory
Descotes-Genon, S
2008-01-01
The (light but not-so-light) strange quark may play a special role in the low-energy dynamics of QCD. The presence of strange quark pairs in the sea may have a significant impact of the pattern of chiral symmetry breaking : in particular large differences can occur between the chiral limits of two and three massless flavours (i.e., whether m_s is kept at its physical value or sent to zero). This may induce problems of convergence in three-flavour chiral expansions. To cope with such difficulties, we introduce a new framework, called Resummed Chiral Perturbation Theory. We exploit it to analyse pi-pi and pi-K scatterings and match them with dispersive results in a frequentist framework. Constraints on three-flavour chiral order parameters are derived.
Heavy quark bound states in a quark-gluon plasma: dissociation and recombination
Blaizot, Jean-Paul; Faccioli, Pietro; Garberoglio, Giovanni
2015-01-01
We present a comprehensive approach to the dynamics of heavy quarks in a quark gluon plasma, including the possibility of bound state formation and dissociation. In this exploratory paper, we restrict ourselves to the case of an Abelian plasma, but the extension of the techniques used to the non Abelian case is straightforward. A chain of well defined approximations leads eventually to a generalized Langevin equation, where the force and the noise terms are determined from a correlation function of the equilibrium plasma, and depend explicitly on the configuration of the heavy quarks. We solve the Langevin equation for various initial conditions, various numbers of heavy quark-antiquark pairs, and various temperatures of the plasma. Results of simulations illustrate various expected phenomena: dissociation of bound states as a result of combined effects of screening of the potential and collisions with the plasma constituent, formation of bound pairs (recombination) that occurs when enough heavy quarks are pr...
The NJL Model for Quark Fragmentation Functions
Energy Technology Data Exchange (ETDEWEB)
T. Ito, W. Bentz, I. Cloet, A W Thomas, K. Yazaki
2009-10-01
A description of fragmentation functions which satisfy the momentum and isospin sum rules is presented in an effective quark theory. Concentrating on the pion fragmentation function, we first explain the reason why the elementary (lowest order) fragmentation process q → qπ is completely inadequate to describe the empirical data, although the “crossed” process π → qq describes the quark distribution functions in the pion reasonably well. Then, taking into account cascade-like processes in a modified jet-model approach, we show that the momentum and isospin sum rules can be satisfied naturally without introducing any ad-hoc parameters. We present numerical results for the Nambu-Jona-Lasinio model in the invariant mass regularization scheme, and compare the results with the empirical parametrizations. We argue that this NJL-jet model provides a very useful framework to calculate the fragmentation functions in an effective chiral quark theory.
Cheshire cat phenomena and quarks in nuclei
International Nuclear Information System (INIS)
The notion of the ''Cheshire Cat'' principle in hadron structure is developed rigorously in (1+1) dimensions and approximately in (3+1) dimensions for up- and down-quark flavor systems. This phenomenon is invoked to address the issue as to whether or not direct quark-gluon signatures can be ''seen'' in low-energy nuclear phenomena. How addition of the third flavor -strangeness- can modify the Cheshire Cat property is discussed. It is proposed that one of the primary objectives of nuclear physics be to probe -and disturb- the ''vacuum'' of the strong interactions (QCD) and that for this purpose the chiral symmetry SU(3)xSU(3) can play a crucial role in normal and extreme conditions. As an illustration, kaon condensation at a density ρ>∼ 3ρ0 is discussed in terms of a toy model and is related to ''cleansing'' of the quark condensates from the vacuum